I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being
solid state there really isn't much of a warm-up so I am lost.... Anyone
got any ideas how to isolate the problem?
wb

When parts become temperature sensitive with age, it does not take much
to have drift, especially in the frequency range used for FM reception.

It is very possible that one of the small caps, or resistors, or the
local oscillator transistor itself is changing value. A tech with a lot
of experience in high frequency RF troubleshooting can easily service
this for you. I would not recommend for you to mess around in the front
end of your receiver, unless you really know what you are doing, and
have the necessary test gear to know exactly what is going on. This
section is so sensitive, that re-soldering components can change the
tuning of it.

After replacing the defective parts, tech should do a re-calibration of
the front end to make sure that it is performing to specs.

--

Jerry G.


"wß" wrote in message
...
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being
solid state there really isn't much of a warm-up so I am lost.... Anyone
got any ideas how to isolate the problem?
wb

[Phil Allison]

"wß"

I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up.


** FM tuners all drift with temperature, excepting the newer ones with
synthesised frequency control.


I first thought it was the regulated 13.2 volts but substituted an
external voltage source and that made no difference. I gently blew the
dust off the tuning cap. Being solid state there really isn't much of a
warm-up so I am lost.... Anyone got any ideas how to isolate the problem?


** What problem exactly ?

How much does it drift ?

A drift of say 100kHz to 200 kHz from cold would be good performance -
consistent with an oscillator stability of 100 to 200 ppm per degree C.

Most tuners have an AFC button to fix this.




........ Phil

[Trevor Wilson]

"wß" wrote in message
...
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being solid
state there really isn't much of a warm-up so I am lost.... Anyone got any
ideas how to isolate the problem?
wb

**This is a major PITA. The old Marantz tuners and receivers were fitted
with carefully selected capacitors, whose temperature drift was precisely
chosen to complement the drift in the associated coils. They were impossible
to buy from Marantz back in the 1970s, so would be difficult to obtain now.
I solved the problem in a few units, by building a crystal locked AFC
circuit. Expensive, but worth it for the models I performed the mod on.
Realistically, I suggest you forget it, as it is too difficult a problem to
solve.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Mark D. Zacharias]

Trevor Wilson wrote:
"wß" wrote in message
...
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and
that made no difference. I gently blew the dust off the tuning cap.
Being solid state there really isn't much of a warm-up so I am
lost.... Anyone got any ideas how to isolate the problem?
wb

**This is a major PITA. The old Marantz tuners and receivers were
fitted with carefully selected capacitors, whose temperature drift
was precisely chosen to complement the drift in the associated coils.
They were impossible to buy from Marantz back in the 1970s, so would
be difficult to obtain now. I solved the problem in a few units, by
building a crystal locked AFC circuit. Expensive, but worth it for
the models I performed the mod on. Realistically, I suggest you
forget it, as it is too difficult a problem to solve.


--
Trevor Wilson
www.rageaudio.com.au

Try freeze-mist to help locate the temperature-sensitive component (probably
a capacitor). I think most FM tuner sections had AFC circuits, though most
stereo receivers DID NOT have defeatable switches for this once PLL circuits
evolved. Could be an AFC / PLL problem more than a front-end or local
oscillator problem.


Mark Z.

[Phil Allison]

"Mark D. Zacharias"


Try freeze-mist to help locate the temperature-sensitive component
(probably a capacitor).


** Ignore this asinine fool.

He has no comprehension of oscillator circuits.



I think most FM tuner sections had AFC circuits, though most stereo
receivers DID NOT have defeatable switches for this once PLL circuits
evolved.


** PLL frequency synthesisers ELIMINATE the need for AFC completely.


Could be an AFC / PLL problem more than a front-end or local oscillator
problem.


** Or just NORMAL warm up drift.




........ Phil

[wß]

Phil Allison wrote:
"wß"
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up.


** FM tuners all drift with temperature, excepting the newer ones with
synthesised frequency control.

Of my collection this is the only one that drifts. In fact, when I
was in the business, the only ones I ever recall with a drift problem
was one or two Fisher's with the varactor tuning crap.



I first thought it was the regulated 13.2 volts but substituted an
external voltage source and that made no difference. I gently blew the
dust off the tuning cap. Being solid state there really isn't much of a
warm-up so I am lost.... Anyone got any ideas how to isolate the problem?


** What problem exactly ?

Uhhhhm, that would be the drifting off center frequency problem...


How much does it drift ?


Considering that the bandwidth of an FM broadcast channel is ±75KHz I
would guess that it is wandering high between 25 and 45 KHz as the
clarity of sound isn't much affected but of course the mute will kick in.

A drift of say 100kHz to 200 kHz from cold would be good performance -
consistent with an oscillator stability of 100 to 200 ppm per degree C.

Not in my world! Although I suppose it depends on what you call cold
and hot. Within a designed operating temperature range I expect an
oscillator to be on frequency.


Most tuners have an AFC button to fix this.

Yeah, Yeah I know. I suppose but Vintage Marantz receivers worked pretty
well without. I am partial to the type Radio Shack used. The Accutune, I
think it was called, switched off when you touched the tuning knob. Nice
touch.





....... Phil



I've already spent too much time on this post...
.... wb

[wß]

Trevor Wilson wrote:
"wß" wrote in message
...
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being solid
state there really isn't much of a warm-up so I am lost.... Anyone got any
ideas how to isolate the problem?
wb

**This is a major PITA. The old Marantz tuners and receivers were fitted
with carefully selected capacitors, whose temperature drift was precisely
chosen to complement the drift in the associated coils. They were impossible
to buy from Marantz back in the 1970s, so would be difficult to obtain now.
I solved the problem in a few units, by building a crystal locked AFC
circuit. Expensive, but worth it for the models I performed the mod on.
Realistically, I suggest you forget it, as it is too difficult a problem to
solve.


Thanks for the tip. Maybe I'll swap out the front end and not obsess
over it. If I can find a cheap doner unit on eBay...

[wß]

Mark D. Zacharias wrote:
Trevor Wilson wrote:
"wß" wrote in message
...
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and
that made no difference. I gently blew the dust off the tuning cap.
Being solid state there really isn't much of a warm-up so I am
lost.... Anyone got any ideas how to isolate the problem?
wb
**This is a major PITA. The old Marantz tuners and receivers were
fitted with carefully selected capacitors, whose temperature drift
was precisely chosen to complement the drift in the associated coils.
They were impossible to buy from Marantz back in the 1970s, so would
be difficult to obtain now. I solved the problem in a few units, by
building a crystal locked AFC circuit. Expensive, but worth it for
the models I performed the mod on. Realistically, I suggest you
forget it, as it is too difficult a problem to solve.


--
Trevor Wilson
www.rageaudio.com.au

Try freeze-mist to help locate the temperature-sensitive component (probably
a capacitor). I think most FM tuner sections had AFC circuits, though most
stereo receivers DID NOT have defeatable switches for this once PLL circuits
evolved. Could be an AFC / PLL problem more than a front-end or local
oscillator problem.


Mark Z.



I would need a very tiny tube to make freeze-mist type diagnostics, but
thanks for the thought. Yeah, I wish it was in the AFC loop. But there
is none. The only connection from the FE to the IF strip is the IF
output from the FE. This could be a problem with the ratio-detector, I
suppose, but I was just hoping that maybe this was somewhat of a
commonly observed problem.

[Phil Allison]

"wß"

I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up.


** FM tuners all drift with temperature, excepting the newer ones with
synthesised frequency control.

Of my collection this is the only one that drifts.


** You are clearly a damn liar.



I first thought it was the regulated 13.2 volts but substituted an
external voltage source and that made no difference. I gently blew the
dust off the tuning cap. Being solid state there really isn't much of a
warm-up so I am lost.... Anyone got any ideas how to isolate the
problem?


** What problem exactly ?

Uhhhhm, that would be the drifting off center frequency problem...


** Wot a smartarse liar.



How much does it drift ?


Considering that the bandwidth of an FM broadcast channel is ±75KHz I
would guess that it is wandering high between 25 and 45 KHz as the clarity
of sound isn't much affected but of course the mute will kick in.


** That is a very small drift.

Typical of a good VHF oscillator, uncorrected by AFC, during warm up.



A drift of say 100kHz to 200 kHz from cold would be good performance -
consistent with an oscillator stability of 100 to 200 ppm per degree C.

Not in my world!


** So this lying asshole lives on another planet.

Suspected as much.


Although I suppose it depends on what you call cold and hot. Within a
designed operating temperature range I expect an oscillator to be on
frequency.


** Expect all you like - asshole.



Most tuners have an AFC button to fix this.

Yeah, Yeah I know.


** Then stop being a PRICK and realise there IS a very basic reason for
them.



I suppose but Vintage Marantz receivers worked pretty well without.


** As does your 2240B - ****wit.




........ Phil

[Phil Allison]

"wß"


Thanks for the tip. Maybe I'll swap out the front end and not obsess over
it. If I can find a cheap doner unit on eBay...



** Go ahead - make my day ...

You pathetic bloody ******.





......... Phil

[Trevor Wilson]

"Mark D. Zacharias" wrote in message
. net...
Trevor Wilson wrote:
"wß" wrote in message
...
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and
that made no difference. I gently blew the dust off the tuning cap.
Being solid state there really isn't much of a warm-up so I am
lost.... Anyone got any ideas how to isolate the problem?
wb

**This is a major PITA. The old Marantz tuners and receivers were
fitted with carefully selected capacitors, whose temperature drift
was precisely chosen to complement the drift in the associated coils.
They were impossible to buy from Marantz back in the 1970s, so would
be difficult to obtain now. I solved the problem in a few units, by
building a crystal locked AFC circuit. Expensive, but worth it for
the models I performed the mod on. Realistically, I suggest you
forget it, as it is too difficult a problem to solve.


--
Trevor Wilson
www.rageaudio.com.au

Try freeze-mist to help locate the temperature-sensitive component
(probably a capacitor). I think most FM tuner sections had AFC circuits,
though most stereo receivers DID NOT have defeatable switches for this
once PLL circuits evolved. Could be an AFC / PLL problem more than a
front-end or local oscillator problem.

**Marantz never used AFC in their tuners, back then. PLL was only used for
stereo FM decoding, as was normal practice.


--
Trevor Wilson
www.rageaudio.com.au



--
Posted via a free Usenet account from http://www.teranews.com

[Mark D. Zacharias]

Phil Allison wrote:
"Mark D. Zacharias"


Try freeze-mist to help locate the temperature-sensitive component
(probably a capacitor).


** Ignore this asinine fool.

He has no comprehension of oscillator circuits.



I think most FM tuner sections had AFC circuits, though most stereo
receivers DID NOT have defeatable switches for this once PLL circuits
evolved.


** PLL frequency synthesisers ELIMINATE the need for AFC
completely.

Could be an AFC / PLL problem more than a front-end or local
oscillator problem.


** Or just NORMAL warm up drift.




....... Phil

Excuse me Phil, I have personally found temperature sensitive capacitors
this way, fixing for example Pioneer receivers with drift problems.

I sort of run these circuits together - PLL, AFC, etc. Sorry I wasn't more
clear.

"normal warmup drift" is exactly what PLL was designed to eliminate. I used
to have a Heath AJ-41 tube tuner which had the phase control on the front
panel. Needed to be re-adjusted after a few minutes warmup. I've owned and
used dozens of solid state tuners over the years and never seen a properly
funtioning one require more than the most miniscule re-tuning after warmup.


Mark Z.

[Phil Allison]

"Mark D. Zacharias"

Try freeze-mist to help locate the temperature-sensitive component
(probably a capacitor).


** Ignore this asinine fool.

He has no comprehension of oscillator circuits.



I think most FM tuner sections had AFC circuits, though most stereo
receivers DID NOT have defeatable switches for this once PLL circuits
evolved.


** PLL frequency synthesisers ELIMINATE the need for AFC
completely.


Could be an AFC / PLL problem more than a front-end or local
oscillator problem.


** Or just NORMAL warm up drift.


Excuse me Phil, I have personally found temperature sensitive capacitors
this way, fixing for example Pioneer receivers with drift problems.


** But not frequency drift inherent in the local oscillator itself.


I sort of run these circuits together - PLL, AFC, etc.


** The tuner in the receiver concerned HAS no AFC.


I've owned and used dozens of solid state tuners over the years and never
seen a properly funtioning one require more than the most miniscule
re-tuning after warmup.


** That is only true for those tuners that simply do not warm up - ie
where the unit remains at room temp whether on or off.




........ Phil

[GregS]

In article , none wrote:
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being
solid state there really isn't much of a warm-up so I am lost.... Anyone
got any ideas how to isolate the problem?
wb

The drift is probably temperature, and thats how you troubleshoot. Get a can of
freeze and something with heat. A soldering iron near parts works.

greg

[Phil Allison]

"GregS"

In article , none wrote:
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being
solid state there really isn't much of a warm-up so I am lost.... Anyone
got any ideas how to isolate the problem?
wb

The drift is probably temperature, and thats how you troubleshoot.



** All of 25 kHz ( according to the OP) over a 30 minute warm up in a base
frequency of 100Mhz !!!!!

That = 250 parts per million in maybe a 10 degree C temp rise.

= 25 ppm per C !!!

Only a crystal oscillator at 1 or 2 ppm per C has better stability.






........ Phil

[GregS]

In article , "Phil Allison" wrote:

"GregS"

In article , none wrote:
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being
solid state there really isn't much of a warm-up so I am lost.... Anyone
got any ideas how to isolate the problem?
wb

The drift is probably temperature, and thats how you troubleshoot.



** All of 25 kHz ( according to the OP) over a 30 minute warm up in a base
frequency of 100Mhz !!!!!

That = 250 parts per million in maybe a 10 degree C temp rise.

= 25 ppm per C !!!

Only a crystal oscillator at 1 or 2 ppm per C has better stability.

The guy didn't specify how much. I guess the center tune meter goes off.
I think they all drift somewhat. He also didn't say if it has an effect other than
visual.

greg

[Phil Allison]

"GregS

The drift is probably temperature, and thats how you troubleshoot.



** All of 25 kHz ( according to the OP) over a 30 minute warm up in a
base
frequency of 100Mhz !!!!!

That = 250 parts per million in maybe a 10 degree C temp rise.

= 25 ppm per C !!!

Only a crystal oscillator at 1 or 2 ppm per C has better stability.

The guy didn't specify how much.


** YES he *bloody* did.

READ the WHOLE damn thread !!!



I guess the center tune meter goes off.
I think they all drift somewhat. He also didn't say if it has an effect
other than
visual.


** HE did say that TOO.

Read ALL the OPs posts !!


BTW

You know NOTHING about the topic.

Bloody NG parasite !!!




......... Phil

[GregS]

In article , "Phil Allison" wrote:

"GregS

The drift is probably temperature, and thats how you troubleshoot.



** All of 25 kHz ( according to the OP) over a 30 minute warm up in a
base
frequency of 100Mhz !!!!!

That = 250 parts per million in maybe a 10 degree C temp rise.

= 25 ppm per C !!!

Only a crystal oscillator at 1 or 2 ppm per C has better stability.

The guy didn't specify how much.


** YES he *bloody* did.

READ the WHOLE damn thread !!!

I found it!

The real answer may be very difficult to find. Sometimes there
are components used to counter heat drift. Any specs may be off.
Many of the parts will be temperature specific, so you would have to know everything
about the circuit, but sometimes you get lucky or not.


I guess the center tune meter goes off.
I think they all drift somewhat. He also didn't say if it has an effect
other than
visual.


** HE did say that TOO.

Read ALL the OPs posts !!


BTW

You know NOTHING about the topic.

Bloody NG parasite !!!




......... Phil

[Phil Allison]

"GregS"


** **** off - IDIOT !




........ Phil

[Chuck]

On Sun, 02 Jul 2006 22:40:00 GMT, "Mark D. Zacharias"
wrote:

Phil Allison wrote:
"Mark D. Zacharias"


Try freeze-mist to help locate the temperature-sensitive component
(probably a capacitor).


** Ignore this asinine fool.

He has no comprehension of oscillator circuits.



I think most FM tuner sections had AFC circuits, though most stereo
receivers DID NOT have defeatable switches for this once PLL circuits
evolved.


** PLL frequency synthesisers ELIMINATE the need for AFC
completely.

Could be an AFC / PLL problem more than a front-end or local
oscillator problem.


** Or just NORMAL warm up drift.




....... Phil

Excuse me Phil, I have personally found temperature sensitive capacitors
this way, fixing for example Pioneer receivers with drift problems.

I sort of run these circuits together - PLL, AFC, etc. Sorry I wasn't more
clear.

"normal warmup drift" is exactly what PLL was designed to eliminate. I used
to have a Heath AJ-41 tube tuner which had the phase control on the front
panel. Needed to be re-adjusted after a few minutes warmup. I've owned and
used dozens of solid state tuners over the years and never seen a properly
funtioning one require more than the most miniscule re-tuning after warmup.


Mark Z.



We used to have that problem too with Pioneer receivers back in the
late 70s. Rarely we had to use npo capacitors that changed
capacitance in the opposite direction from the other caps in the
oscillator circuit to counteract warm up drift. Back then the company
I worked for wouldn't allow us not to repair an item or send it back
to the factory for service, so we'd sub a cap, let it warm up an hour
and then try a different cap in the same location until the drift rate
was acceptable. Since we were all on commission, we loved these
receivers. Chuck

[Vivek]

The program Smith has grown beyond your control. Soon he will spread through
this city, as he has spread through the Matrix. You cannot stop him...

"Phil Allison" wrote in message
...
|
| "GregS"
|
|
| ** **** off - IDIOT !
|
|
|
|
| ....... Phil
|
|
|

[wiz82]

wß wrote:
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being
solid state there really isn't much of a warm-up so I am lost.... Anyone
got any ideas how to isolate the problem?
wb

I'm surprised that none of you internet rocket scientists are even
close to resolving
the most common problem with the alps tuning caps used in many of the
vintage fm tuners. Simply clean the oxidation off the wipers in each
section of the fm tuning cap
( the fewer wider spaced plates ) Yes it could be an electronic
component, but in my
extensive experience ( 30+ years consumer and pro audio service ) I'm
willing to bet the wipers in the main tuning cap assy are the true
culprits

[wß]

wiz82 wrote:
wß wrote:
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being
solid state there really isn't much of a warm-up so I am lost.... Anyone
got any ideas how to isolate the problem?
wb

I'm surprised that none of you internet rocket scientists are even
close to resolving
the most common problem with the alps tuning caps used in many of the
vintage fm tuners. Simply clean the oxidation off the wipers in each
section of the fm tuning cap
( the fewer wider spaced plates ) Yes it could be an electronic
component, but in my
extensive experience ( 30+ years consumer and pro audio service ) I'm
willing to bet the wipers in the main tuning cap assy are the true
culprits


Makes more sense than a cap "gone bad". Though I can't imagine how dirty
plates could be temperature sensitive. I managed to score a cheap doner
unit for a front end but I will try your suggestion first. I am not in
any mood to be shotgunning tiny capacitors. What would you suggest as a
cleaning agent? 99% alcohol or CFC. Though not PC I find that CFC is an
excellent cleaner. 99% alcohol seems to work well in most instances too.

[Bob Urz]

wß wrote:

wiz82 wrote:

wß wrote:

I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being
solid state there really isn't much of a warm-up so I am lost.... Anyone
got any ideas how to isolate the problem?
wb


I'm surprised that none of you internet rocket scientists are even
close to resolving
the most common problem with the alps tuning caps used in many of the
vintage fm tuners. Simply clean the oxidation off the wipers in each
section of the fm tuning cap
( the fewer wider spaced plates ) Yes it could be an electronic
component, but in my
extensive experience ( 30+ years consumer and pro audio service ) I'm
willing to bet the wipers in the main tuning cap assy are the true
culprits


Makes more sense than a cap "gone bad". Though I can't imagine how dirty
plates could be temperature sensitive. I managed to score a cheap doner
unit for a front end but I will try your suggestion first. I am not in
any mood to be shotgunning tiny capacitors. What would you suggest as a
cleaning agent? 99% alcohol or CFC. Though not PC I find that CFC is an
excellent cleaner. 99% alcohol seems to work well in most instances too.

I usually spray the plate contact areas with Caig d5 or pro gold.
No guarantees, but it usually makes it better.
Work the control back and forth for a few minutes after you spray it.
And don't break the dam dial string........



Bob

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

[wiz82]

wß wrote:
wiz82 wrote:
wß wrote:
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being
solid state there really isn't much of a warm-up so I am lost.... Anyone
got any ideas how to isolate the problem?
wb

I'm surprised that none of you internet rocket scientists are even
close to resolving
the most common problem with the alps tuning caps used in many of the
vintage fm tuners. Simply clean the oxidation off the wipers in each
section of the fm tuning cap
( the fewer wider spaced plates ) Yes it could be an electronic
component, but in my
extensive experience ( 30+ years consumer and pro audio service ) I'm
willing to bet the wipers in the main tuning cap assy are the true
culprits


Makes more sense than a cap "gone bad". Though I can't imagine how dirty
plates could be temperature sensitive. I managed to score a cheap doner
unit for a front end but I will try your suggestion first. I am not in
any mood to be shotgunning tiny capacitors. What would you suggest as a
cleaning agent? 99% alcohol or CFC. Though not PC I find that CFC is an
excellent cleaner. 99% alcohol seems to work well in most instances too.

Keep in mind that a tuned circuit ie. RF amp ,mixer & Local Osc in a
typical vintage FM front end consists of inductance , capacitive and to
a lesser degree resistance. The brass or in some cases silver plated
wipers which ground each section of the main variable tuning cap are
almost always greased when new as a means to retard oxidation. As the
set ages, the grease drys out and often does two things - it either
breaks the ground connection alltogeather, or adds a varying resistance
( changed by temp or humidity ) Use a strong degreasing solvent I use
Ensolve - about $80.00 / gal compressed air and small brushes to get
rid of the crap on the wipers. All the while
one must move the tuning cap back & forth to allow the cleaned up
wipers to bear against the mating section of the tuning cap section ( 3
in a basic set, 5 to 8 in a high end tuner ) By the way if you can
find it, the old formulation of Tunowash works well
but has not been sold for years due to its high CFC content. Any how I
have restored so
many sets " condemmed " as needing complete front end assy's by using
this method.
The only other thing I might add at this point is I have seen a number
of Alps frontends
drift where the local osc transistor is the old Hitachi "wedge" style
2SC535 I think but don't flame me if I got the number wrong. Anyho the
thing to look for is if you see what appears to be a black fluffy
residue covering the leads of the transistor Change it !!
This process also creates of alot of weird audio problems in Kenwood
vintage stuff as
well. I gather oxidation and or moisture creeps up the leads of the
transistor gets into the device and changes its operating
characteristics any of us old time audio techs have
seen this a bunch

[Mark D. Zacharias]

wiz82 wrote:
wß wrote:
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and
that made no difference. I gently blew the dust off the tuning cap.
Being solid state there really isn't much of a warm-up so I am
lost.... Anyone got any ideas how to isolate the problem?
wb

I'm surprised that none of you internet rocket scientists are even
close to resolving
the most common problem with the alps tuning caps used in many of the
vintage fm tuners. Simply clean the oxidation off the wipers in each
section of the fm tuning cap
( the fewer wider spaced plates ) Yes it could be an electronic
component, but in my
extensive experience ( 30+ years consumer and pro audio service ) I'm
willing to bet the wipers in the main tuning cap assy are the true
culprits

Sometimes we have to get hit over the head.

:-)

I haven't seen drift problems as such from the aforementioned wipers, but I
have seen noisy, erratic tuning characteristics, which could also relate to
the OP's problem, even to the extent of being temperature sensitive.

I use Caig D-100 non-aerosol, and drip it into where the copper feelers
contact the center shaft of the tuning cap. Work it around a bit as you say,
that particular problem solved. The last one I did was an Accuphase T-100.


Mark Z

[wß]

Wiz82 wrote:
wß wrote:
wiz82 wrote:
wß wrote:
I've a Marantz 2240B that drifts on the FM with warm up over about 30
minutes. Seems to be stable after warm-up. I first thought it was the
regulated 13.2 volts but substituted an external voltage source and that
made no difference. I gently blew the dust off the tuning cap. Being
solid state there really isn't much of a warm-up so I am lost.... Anyone
got any ideas how to isolate the problem?
wb
I'm surprised that none of you internet rocket scientists are even
close to resolving
the most common problem with the alps tuning caps used in many of the
vintage fm tuners. Simply clean the oxidation off the wipers in each
section of the fm tuning cap
( the fewer wider spaced plates ) Yes it could be an electronic
component, but in my
extensive experience ( 30+ years consumer and pro audio service ) I'm
willing to bet the wipers in the main tuning cap assy are the true
culprits

Makes more sense than a cap "gone bad". Though I can't imagine how dirty
plates could be temperature sensitive. I managed to score a cheap doner
unit for a front end but I will try your suggestion first. I am not in
any mood to be shotgunning tiny capacitors. What would you suggest as a
cleaning agent? 99% alcohol or CFC. Though not PC I find that CFC is an
excellent cleaner. 99% alcohol seems to work well in most instances too.

Keep in mind that a tuned circuit ie. RF amp ,mixer & Local Osc in a
typical vintage FM front end consists of inductance , capacitive and to
a lesser degree resistance. The brass or in some cases silver plated
wipers which ground each section of the main variable tuning cap are
almost always greased when new as a means to retard oxidation. As the
set ages, the grease drys out and often does two things - it either
breaks the ground connection alltogeather, or adds a varying resistance
( changed by temp or humidity ) Use a strong degreasing solvent I use
Ensolve - about $80.00 / gal compressed air and small brushes to get
rid of the crap on the wipers. All the while
one must move the tuning cap back & forth to allow the cleaned up
wipers to bear against the mating section of the tuning cap section ( 3
in a basic set, 5 to 8 in a high end tuner ) By the way if you can
find it, the old formulation of Tunowash works well
but has not been sold for years due to its high CFC content. Any how I
have restored so
many sets " condemmed " as needing complete front end assy's by using
this method.
The only other thing I might add at this point is I have seen a number
of Alps frontends
drift where the local osc transistor is the old Hitachi "wedge" style
2SC535 I think but don't flame me if I got the number wrong. Anyho the
thing to look for is if you see what appears to be a black fluffy
residue covering the leads of the transistor Change it !!
This process also creates of alot of weird audio problems in Kenwood
vintage stuff as
well. I gather oxidation and or moisture creeps up the leads of the
transistor gets into the device and changes its operating
characteristics any of us old time audio techs have
seen this a bunch


It is a 2SC535b transistor so I will watch for that also. Thanks for the
tips. I do have an idea of what I am doing as I worked on consumer
equipment in the 70's & 80's. Never saw these kind of problems when the
stuff was still new... In fact, seems like most of the problems we saw
were caused by the user himself! Thanks again and if it turns into a
nightmare or an outrageous success I will post again for the sake of the
group and some other poor soul faced with a similar problem.

[Phil Allison]

"wß"


** **** off - TROLL.







......... Phil