[[email protected]]

Hi,
I recently picked up a Grundig console stereo with hi fi. It turns on
and I can get reception, but makes loud popping noises when I switch
between bands. Also, after running for a few minutes the sound starts
to go in and out and will sometimes die altogether. I'd like to get it
repaired so that at least the FM band works consistently. Due to the
size however, I'd prefer a house call or do the repair myself. But I
don't know where to begin in diagnosing what is wrong. Can anyone help
me out here? I'm in Arlington, VA outside of DC.

The following on EBay is the same (or very similar) radio, although
housed in a different console.
http://tinyurl.com/jnaob

Will trade freshly roasted (home roasted) coffee in exchange for your
repair or diagnosing expertise.

Thanks
Chris

[Sander deWaal]

said:

Hi,
I recently picked up a Grundig console stereo with hi fi. It turns on
and I can get reception, but makes loud popping noises when I switch
between bands. Also, after running for a few minutes the sound starts
to go in and out and will sometimes die altogether. I'd like to get it
repaired so that at least the FM band works consistently. Due to the
size however, I'd prefer a house call or do the repair myself. But I
don't know where to begin in diagnosing what is wrong. Can anyone help
me out here? I'm in Arlington, VA outside of DC.

The following on EBay is the same (or very similar) radio, although
housed in a different console.
http://tinyurl.com/jnaob

Will trade freshly roasted (home roasted) coffee in exchange for your
repair or diagnosing expertise.


While I'm far, far away from you ( The Netherlands), I may be of some
help:
Start with replacing all electrolytics, and coupling capacitors
between stages.

Lubricate the switches with a suitable spray.

If the FM front end is equipped with a ECC85, open up the case where
it sits on, and check the various resistors for drifted values.
Especially the grid resistor in the oscillator section (which is
220kohm IIRC) is important.

If the oscillator works again (you should hear noise coming out of the
speaker), check if it oscillates across the entire FM band.
If not, either the ECC85 is nearly dead, or the high voltage is too
low.
Replace the ECC85 with a known good one.
Clean out the variable capacitor with compressed air (careful, not too
much pressure), and lubricate the bearings and contact rings/sleeves.

Depending on year and model, rectifying may be with an EZ81 or a metal
rectifier ( siemens "Flachengleichrichter" ).
Expect the high voltage to be somewhere in the 280 V region.

that's probably a good start, and for someone with some tube
knowledge, it is fairly easy to do.

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Eeyore]

Peter Wieck wrote:

These commonly suffer from "lazy cathode", the radio
being left on AM or SW all the time with the tube hot and not emitting,
contaminating the cathode... whether this is the exact process, it is
certainly a common result.

You mean no anode ( plate ) volts ?


Graham

[Peter Wieck]

wrote:
Hi,
I recently picked up a Grundig console stereo with hi fi. It turns on
and I can get reception, but makes loud popping noises when I switch
between bands. Also, after running for a few minutes the sound starts
to go in and out and will sometimes die altogether. I'd like to get it
repaired so that at least the FM band works consistently. Due to the
size however, I'd prefer a house call or do the repair myself.

Can't drink coffee... violently allergic (I get violent, not sick). But
my wife does.

OK.

Where are you? Did you snag this beast recently at Kutztown?

Start with cleaning the bejesus out of the controls. Next, acquire a
6AQ8 (or several) (US-sub for ECC85) and swap it out. This tube is one
of the most peculiar ever made in terms of what works in which radio,
so you may have to try a couple. Bluntly, this may be all you need. If
this fails, then follow Sander's advice. On no account follow Bret's
advice, it ain't nohow rocket science, and these radios are rather well
built if not overly meddled with by well-meaning amateurs. It MAY need
recapping in any case, but don't go down that road until you have
exhausted all other means and have the diagosis confirmed. Keep also in
mind that a complete recapping will require re-alignment, both of AM
and FM for best performance. Then you will need to trot out Bret's
instruments for the FM side.

If you are getting sound at all, it indicates filthy controls and a
weak 6AQ8/ECC85. These commonly suffer from "lazy cathode", the radio
being left on AM or SW all the time with the tube hot and not emitting,
contaminating the cathode... whether this is the exact process, it is
certainly a common result.

Enjoy,

Peter Wieck
Wyncote, PA

[Peter Wieck]

Eeyore wrote:
Peter Wieck wrote:

These commonly suffer from "lazy cathode", the radio
being left on AM or SW all the time with the tube hot and not emitting,
contaminating the cathode... whether this is the exact process, it is
certainly a common result.

You mean no anode ( plate ) volts ?


Graham

Yes. The filament is hot, but no other voltage is applied. Many AM/FM
Zeniths with the same tube suffered from the same failure for the same
reason. Occasionally, one can overheat the tube and get it to operate,
but that is iffy at best.

Peter Wieck
Wyncote, PA

[Eeyore]

Peter Wieck wrote:

Eeyore wrote:
Peter Wieck wrote:

These commonly suffer from "lazy cathode", the radio
being left on AM or SW all the time with the tube hot and not emitting,
contaminating the cathode... whether this is the exact process, it is
certainly a common result.

You mean no anode ( plate ) volts ?

Yes. The filament is hot, but no other voltage is applied. Many AM/FM
Zeniths with the same tube suffered from the same failure for the same
reason. Occasionally, one can overheat the tube and get it to operate,
but that is iffy at best.

I follow you.

Graham

[Sander deWaal]

Eeyore said:


These commonly suffer from "lazy cathode", the radio
being left on AM or SW all the time with the tube hot and not emitting,
contaminating the cathode... whether this is the exact process, it is
certainly a common result.


You mean no anode ( plate ) volts ?


Yes. The filament is hot, but no other voltage is applied. Many AM/FM
Zeniths with the same tube suffered from the same failure for the same
reason. Occasionally, one can overheat the tube and get it to operate,
but that is iffy at best.


I follow you.


There's also something called "Sleeping Sickness" where the reverse
may cause trouble as well.
..
Here's a post by DesertBob from a while ago about this subject:


[quote]
--------------------------------------------------------------------------------------------------------------------

Bob, are you sure "Sleeping sickness" also occurs when B+ is applied
without "filament" power? I never heard of that before, although that
clearly doesn't mean it doesn't happen. snip

Yes, it does! I witnessed this happen one time which resulted in an
supervisor earning a little unpaid vacation time.

Old multiplex equipment associated with Types J, K and L carrier
systems used by AT&T's various companies built in the '40s and '50s
used basically two tubes...the 311B triode, and the 310A sharp cutoff
pentode, essentially a five prong, 5 V filament 6C6, for anything
below the mastergroup MUX level. Above that, the 404A (basically a 5V
6AK5) and the 417A single triode were used for mastergroup gain and
stacking. One day, a migration to IC-based equipment on another floor
occurred in our office, the largest carrier office in the US,
rendering an entire floor's worth of antique channel modems, group
demods, supergroup demods and all associated equipment such as carrier
supplies to be relegated to "spare" status. A transmission man
working that floor, trying to earn a few "brownie" points,
disconnected all the -24V filament battery at the BDFB to all this
gear. Laziness and timidity precluded him from removing the +130 and
+315 plate supplies. Thus, over 750 311B and 310A tubes were left in
situ with their usual B+ on the plates and cold filaments.

About three months later, a surge in traffic demand prompted the
circuit provision bureau to reassign new multiplex facilities to this
equipment, and within a short lead time. When such work happens, the
"circuit order" worker tests the gear both directions, sets levels as
appropriate and checks for basic transmission impediments. In this
case, the equipment didn't pass tone anywhere and wouldn't mod or
demod anything at all, and a trip to the BDFB found boxes of 1 1/3 amp
grasshopper fuses all placed neatly on the floor in front of the fuse
bay. After replacing all the filament supply fuses, the equipment
still failed, but some of it would pass modulated/demodulated signal,
but at bad levels and with not nearly enough gain to meet
specifications. After some checking, they called me down to try to
figure what happened.

Western Electric gear from that era used an "in service" tube test
regimen that looked basically at plate and filament current and
"filament activity" (an old term that really meant "cathode activity"
in anything other than direct heated tubes.) The in service tests
showed acceptable filament current, but the plate current was either
gone or very weak. In cases where there was at least some plate
current, dropping the filament current 10% wouldn't cause a dip in the
plate current...odd. A trip to the Hickok Cardmatic (KS version, of
course) showed all the tubes on the entire floor to be "dead" for Gm.
That's when the "brownie" said, "Oh...well, I took all the filament
fuses out of everything to save power. I reported it to my boss, and
he put an attaboy in my folder." A little investigation proved this
to be true, and the supervisor was given some time off for being an
idiot. A look at the Bell System Practices relating to vacuum tubes
specifically stated that at no time should any tube of any
configuration, except for cold cathode tubes, be allowed to stand with
B+ on any element without the filament being hot.

Some further investigation with the folks at the Littleton, CO WECO
tube plant confirmed that running any tube with the plates energized
and no filament will cause the same, or worse, symptoms as "sleeping
sickness" generally attributed to having a tube run in cutoff for long
periods of time. In short, what happens in either case of "sleeping
sickness" is that the plate winds up acting as a getter, thus becoming
unreceptive to electron reception from the cathode after being plated
with contaminents within the envelope. That explained immediately why
the tubes, while testing bad for Gm, tested good for cathode activity.
This was further confirmed by the fact that newer tubes were still at
least conducting something, while tubes that were some 30-40 years old
were completely dead on test, although the records showed their last
"in service" current test to be well within specs. Conversations with
retiring engineers at the tube plant confirmed that no "real life"
vacuum tube had a very good vacuum in it, and even if it had one, it
would be partially destroyed during the initial aging process by
gasification of the tungsten on the filament and thorium from the hot
plates. That's why tubes have getters in them, after all. As the
fellow told me, "You cut off electron flow, and that plate makes a
really attractive getter...the higher the B+, the more it "gets!" Add
to this that the cathode, grids and filaments are all at or near
ground potential, and you see how this can happen to the plates.

In the final tally for this goof, over 350 310A tubes, at $150 a pop,
and 200 some odd 311Bs, at $75 a pop, had to be replaced on an
emergency basis. At the time, Western Electric was getting out of
tube manufacturing altogether, and the assembly and aging lines for
the old ST envelope tubes were out of commission while the equipment
was being sold to Richardson Electronics. As it turned out, a canvass
of toll offices across the country had to be done to mine every
available 310A and 311B, even old "pulls" from retired equipment, to
get the MUX gear back into service. As it was, the due date for the
facility additions was jeopardized by over two months, and the carrier
group responsible for the gear (ours) had to buy all new Richardson
tubes for the offices which gave up their spares. Total cost of the
fiasco: over $130,000. There was little solace in the fact that the
removal of the filament battery saved about $500 in power costs. To
add insult to injury, the equipment only carried the service for
another six months before being finally retired and scrapped.

"Audiophools" worrying about "cathode stripping" has nothing whatever
to do with "sleeping sickness." I've yet to see any "audiophool" who
actually knows how a tube works, anyway. You have to expect this from
people who refer to audio phenomina as "air," "stage," "detail,"
"crispness" and other assorted laughable terms.

dB

Sidebar: On that particular floor resided many old pieces of gear
from the 1930s, including bays of voice order wire equipment
associated with long gone J and K carrier systems. In them were rows
of bayonet based 101D triodes and 201As, most dating from the 1930s,
some from the '40s. All tested good when pulled after 45+ years of
continuous service. I shudder to think what these old things would've
brought today on fraudBay. The secret to long tube life at the phone
company? Running filaments 10% below rated voltage and excellent
quality elements. The Richardson replacements which came later were
nowhere near the quality of any old WECO tube, and WECO tubes made in
the early '80s were almost as bad.

-----------------------------------------------------------------------------------------------------------------------------

[/ quote]

--
"Due knot trussed yore spell chequer two fined awl miss steaks."

[Bob H.]

Peter Wieck wrote:
Eeyore wrote:
Peter Wieck wrote:

These commonly suffer from "lazy cathode", the radio
being left on AM or SW all the time with the tube hot and not emitting,
contaminating the cathode... whether this is the exact process, it is
certainly a common result.

This was a common problem with earlier tube computers which used
standard tubes. I believe the later tube varients developed for
computers had modifications to the cathode formulation to prevent lazy
cathode, as well as reliability, etc.

Bob H.

[David R Brooks]

Bob H. wrote:
Peter Wieck wrote:
Eeyore wrote:
Peter Wieck wrote:

These commonly suffer from "lazy cathode", the radio
being left on AM or SW all the time with the tube hot and not emitting,
contaminating the cathode... whether this is the exact process, it is
certainly a common result.

This was a common problem with earlier tube computers which used
standard tubes. I believe the later tube varients developed for
computers had modifications to the cathode formulation to prevent lazy
cathode, as well as reliability, etc.

From the E88CC data sheet: "The E88CC ... will maintain its emission
capabilities after long periods of operation under cutoff conditions."

[[email protected]]

Hmmm... You guys are all speaking Greek to me. Is there a good basic
beginner's book for this sort of thing that I could pick up at the
library? I have almost zero electronics knowledge. I know the basic
elements from Engineering 101, but that's about it.

I'm in Arlington, VA and I bought the 'beast' off of Craigslist.
Thanks
chris


Peter Wieck wrote:
wrote:
Hi,
I recently picked up a Grundig console stereo with hi fi. It turns on
and I can get reception, but makes loud popping noises when I switch
between bands. Also, after running for a few minutes the sound starts
to go in and out and will sometimes die altogether. I'd like to get it
repaired so that at least the FM band works consistently. Due to the
size however, I'd prefer a house call or do the repair myself.

Can't drink coffee... violently allergic (I get violent, not sick). But
my wife does.

OK.

Where are you? Did you snag this beast recently at Kutztown?

Start with cleaning the bejesus out of the controls. Next, acquire a
6AQ8 (or several) (US-sub for ECC85) and swap it out. This tube is one
of the most peculiar ever made in terms of what works in which radio,
so you may have to try a couple. Bluntly, this may be all you need. If
this fails, then follow Sander's advice. On no account follow Bret's
advice, it ain't nohow rocket science, and these radios are rather well
built if not overly meddled with by well-meaning amateurs. It MAY need
recapping in any case, but don't go down that road until you have
exhausted all other means and have the diagosis confirmed. Keep also in
mind that a complete recapping will require re-alignment, both of AM
and FM for best performance. Then you will need to trot out Bret's
instruments for the FM side.

If you are getting sound at all, it indicates filthy controls and a
weak 6AQ8/ECC85. These commonly suffer from "lazy cathode", the radio
being left on AM or SW all the time with the tube hot and not emitting,
contaminating the cathode... whether this is the exact process, it is
certainly a common result.

Enjoy,

Peter Wieck
Wyncote, PA

[Sander deWaal]

said:

Hmmm... You guys are all speaking Greek to me. Is there a good basic
beginner's book for this sort of thing that I could pick up at the
library? I have almost zero electronics knowledge. I know the basic
elements from Engineering 101, but that's about it.

I'm in Arlington, VA and I bought the 'beast' off of Craigslist.
Thanks
chris


Pull the plug before doing anything, then wait for a few hours to be
sure every electrolytic is discharged.
Start by replacing the 6AQ8 or ECC85 that is in the FM front end.
There's a good chance that your FM section will be alive again.

Then, buy a can of contact cleaner spray and spray a bit in the
contacts of the switches (I assume it is a radio with "teeth" as
switches, right?)
Push them a lot of times to make sure the spray gets inbetween the
contacts.

Any other comments may me useful for someone who knows what he is
doing, from your first post I assumed you knew a bit about tube
technology.

If the above fails, find a good tech or a hobbyist nearby who can fix
your radio.
It's not rocket science, but it takes some time, knowledge and, above
all, dedication and love for this older technology.

--
"Due knot trussed yore spell chequer two fined awl miss steaks."