[Dave xxxx]

one or more output valves start glowing on and off like buggery,
loudspeakers drivers being thrown fully out and back again, loud pops.
this is happening with or without music playing



ta in advance


Dave

[[email protected]]

Dave xxxx wrote:
one or more output valves start glowing on and off like buggery,
loudspeakers drivers being thrown fully out and back again, loud pops.
this is happening with or without music playing



ta in advance


Dave

Much more information is needed:

Type of amp?
*ALL* Tubes involved?
Age of amp?
How long have you had it?
How long has this been happening?
How much do you know about tube-based electronics?
What, if anything has been done to it by you or to your knowledge?

and so forth...

NOTE: Do not screw around inside the amp unless you know what you are
doing. Lethal voltages are present.

Peter Wieck
Wyncote, PA

[Keith G]

" Dave xxxx" wrote in message
k...
one or more output valves start glowing on and off like buggery,
loudspeakers drivers being thrown fully out and back again, loud pops.
this is happening with or without music playing


Is this a stereo amp, if so are both channels playing up? Fixed or cathode
bias?

[Gilbert Bates]

On Wed, 23 Aug 2006 13:05:18 GMT, " Dave xxxx"
wrote:

one or more output valves start glowing on and off like buggery,
loudspeakers drivers being thrown fully out and back again, loud pops.
this is happening with or without music playing



ta in advance


Dave


Leaky coupling cap? You could disconnect the power stage from the
driver stage by lifting out one end of a coupling cap and see if it
clears up...

[Dave xxxx]

Keith G wrote:
" Dave xxxx" wrote in
message k...
one or more output valves start glowing on and off like buggery,
loudspeakers drivers being thrown fully out and back again, loud
pops. this is happening with or without music playing


Is this a stereo amp, if so are both channels playing up? Fixed or
cathode bias?

stereo amplifier and both speakers move

[Keith G]

" Dave xxxx" wrote in message
...
Keith G wrote:
" Dave xxxx" wrote in
message k...
one or more output valves start glowing on and off like buggery,
loudspeakers drivers being thrown fully out and back again, loud
pops. this is happening with or without music playing


Is this a stereo amp, if so are both channels playing up? Fixed or
cathode bias?

stereo amplifier and both speakers move


OK, how many valves per channel, how many of them glow and valve or ss
rectifier?

(Before you even answer, the one valve per channel in a SET is a blessing in
itself!! ;-)

[Alphonso M'buto Chaing]

In article ,
says...

one or more output valves start glowing on and off like buggery,
loudspeakers drivers being thrown fully out and back again, loud pops.
this is happening with or without music playing



ta in advance


Dave


Infra-sonic motor-boating?

[[email protected]]

Keith G wrote:

Keith, All:

We are being had. Based on the information we have to-date, the amp
could be partially under water....

Any/further speculation should be suspended until additional material
is presented.

Peter Wieck
Wyncote, PA

[minus3Db]

Power supply probably.

After checking for dry joints and the obvious, change out the smoothing
cap, if it is electrolyic it may have been damaged by reverse
conection. I would just buy a new cap.

-3db
Dave xxxx wrote:
one or more output valves start glowing on and off like buggery,
loudspeakers drivers being thrown fully out and back again, loud pops.
this is happening with or without music playing



ta in advance


Dave

[Keith G]

wrote in message
ups.com...

Keith G wrote:

Keith, All:

We are being had. Based on the information we have to-date, the amp
could be partially under water....


Absolutely not, Dave's an 'old friend'....



Any/further speculation should be suspended until additional material
is presented.


Which may take a while, he has 'wellness issues' and goes offline from time
to time. It sounds to me like he's got a bit of rampant voltage somewhere
and I'm wondering what's happening with the power supply....???

[[email protected]]

Keith G wrote:
wrote in message
ups.com...

Keith G wrote:

Keith, All:

We are being had. Based on the information we have to-date, the amp
could be partially under water....


Absolutely not, Dave's an 'old friend'....



Any/further speculation should be suspended until additional material
is presented.


Which may take a while, he has 'wellness issues' and goes offline from time
to time. It sounds to me like he's got a bit of rampant voltage somewhere
and I'm wondering what's happening with the power supply....???

That, a broken trace, a shorted cap, a partially melted tube, a dead
bug on the traces...

Too little information, too many possibilities. But I am at least glad
that he is a credible witness.

Peter Wieck
Wyncote, PA

[Bob H.]

Does this amp have fixed bias, coming off of a single bias supply?

Bob H.


Dave xxxx wrote:
one or more output valves start glowing on and off like buggery,
loudspeakers drivers being thrown fully out and back again, loud pops.
this is happening with or without music playing



ta in advance


Dave

[[email protected]]

Keith G wrote:

Which may take a while, he has 'wellness issues' and goes offline from time
to time. It sounds to me like he's got a bit of rampant voltage somewhere
and I'm wondering what's happening with the power supply....???

But nothing he suggests goes to the power-supply, not based on glowing
tubes and pops... that sounds more like a cold solder, short, shorted
tube or similar mechanical/electrical problem vs. an electronic
problem.

We need to know MORE to have a hope of being helpful.

Peter Wieck
Wyncote, PA

[Iain Churches]

wrote in message
ups.com...

Keith G wrote:

Keith, All:

We are being had. Based on the information we have to-date, the amp
could be partially under water....

Any/further speculation should be suspended until additional material
is presented.

Peter. I think you misjudge this poster. He is a familiar name to
many of us, and the source of many interesting posts.

Iain

[Iain Churches]

"Gilbert Bates" wrote in message
...
On Wed, 23 Aug 2006 13:05:18 GMT, " Dave xxxx"
wrote:

one or more output valves start glowing on and off like buggery,
loudspeakers drivers being thrown fully out and back again, loud pops.
this is happening with or without music playing



ta in advance


Dave


Leaky coupling cap? You could disconnect the power stage from the
driver stage by lifting out one end of a coupling cap and see if it
clears up...

If it is common to both channels, I would look to the psu or bias
supply.

[Keith G]

"Iain Churches" wrote in message
. ..

"Gilbert Bates" wrote in message
...
On Wed, 23 Aug 2006 13:05:18 GMT, " Dave xxxx"
wrote:

one or more output valves start glowing on and off like buggery,
loudspeakers drivers being thrown fully out and back again, loud pops.
this is happening with or without music playing



ta in advance


Dave


Leaky coupling cap? You could disconnect the power stage from the
driver stage by lifting out one end of a coupling cap and see if it
clears up...

If it is common to both channels, I would look to the psu or bias
supply.


My thoughts also (as per previous posts)......

[[email protected]]

Iain Churches wrote:

Peter. I think you misjudge this poster. He is a familiar name to
many of us, and the source of many interesting posts.

So I come to find out... but we **STILL** need better information in
order to have a hope at remote diagnosis. I put in my $0.02 in
suggesting that it was an electrical/mechanical problem vs. a P/S
problem, but based on what we have it still could be anything. My
further guess is that most any of us could diagnose this problem in 5
minutes were it on our bench... but it isn't.

Peter Wieck
Wyncote, PA

[Dave xxxx]

Keith G wrote:
Absolutely not, Dave's an 'old friend'....

ta old chap I am piggy in the middle

more information

Primaluna Prologue Two amp has gone mental again, i.e. broken down

It's the same problem as before where one or more output valves start
glowing on and off like buggery, loudspeakers drivers being thrown
fully out and back again, loud pops. this is happening with or
without music playing
specs of amplifier
Power
Frequency Response
THD with AABB
S/N Ratio
Input Impedance
Input Sensitivity
Maximum Gain
Power Consumption
Net Weight
Shipping Weight
Dimensions
Shipping Dimensions
Inputs
Outputs
Tube Complement
40 Watts per channel
20Hz - 30 kHz +/- .5 dB
0,25% @ 1W; less than 1% up to full power
89 dB
65k Ohm
240 mV (for rated power at maximum volume setting)
37,5 dB
300 Watts
37.5 lbs / 17 kg
41.9 lbs / 19 kg
15.5" x 11" x 7.5" / 395 mm x 280 mm x 190 mm (L x W x H)
18.3" x 15" x 12" / 465 mm x 380 mm x 305 mm (L x W x H)
4 pairs RCA
4 & 8 Ohm Speaker Taps
4 x KT-88, 2 x 12AX7, 2 x 12AU7



regards

--
Dave
www.davewhitter.myby.co.uk

Music is Art - Audio is Engineering
Steam is Fun

[Dave xxxx]

Bob H. wrote:
Does this amp have fixed bias, coming off of a single bias supply?

Bob H.

its got "auto bias"

[[email protected]]

Dave xxxx wrote:
Keith G wrote:
Absolutely not, Dave's an 'old friend'....

ta old chap I am piggy in the middle

more information

Primaluna Prologue Two amp has gone mental again, i.e. broken down

It's the same problem as before where one or more output valves start
glowing on and off like buggery, loudspeakers drivers being thrown
fully out and back again, loud pops. this is happening with or
without music playing

OK.. that really does help. I looked up the Owners Manual and spent a
bit of time with it... Allow me to ask a few questions, but I will
still go out on a limb at the end of them.

a) When this happened before, how did you fix it?
b) Or did it go away spontaneously?
c) What have you done so far this time?
d) This made some/little/no difference?
e) Do you have any means to check tube function individually? It would
be nice to be sure that (a) bad tube(s) is(are) not the cause.
f) Has this amp experienced any accident recently? A coffee spill,
miswatered plant, dog lifting its leg, a person sweating over it? (I
have to ask).
g) Is this amp operated with the tube cage in place? Could any foreign
body/insect/bit of dirt gotten into it, with specific reference to the
tube wells?

Now for the climb out onto the limb: I have stated on two prior
occasions that I do not think this is an electronic problem. Given the
vintage of this amp, I am even less inclined to believe it is
electronic.

I do not know how adept you are at repairs, even whether given the
descriptions of others whether you would care to try. But here is where
I would start:

Before doing any of the following: Remove all tubes (valves) and clean
the pins and sockets, Do this one-at-a-time so that they go back to
whence they came. Make sure each one is bottomed and centered in its
socket. If you find anything untoward in this process such as a salt or
carbon track, partially cooked housefly or carbonized dog hairs, you
may have just found the problem. If not:

1. Isolate the amp from all input devices, leaving just your speakers
connected. Verify that they are connected properly, there are no frayed
speaker cord ends or other silliness.
2. Turn on the amp with the volume all the way down, and the selector
set to an arbitrary position to one extreme or the other, say... CD all
the way CC.
3. Turn it on. Time exactly when the problem begins.
4. If there is no problem at the outset, gradually increase the volume
(but *not* past 3/4 way) until it appears. Take your time with this.
5. IF, by some chance, it does not appear, add back one input device
at a time, removing each one in turn before installing the next.
6. Turn off.

Report Back.

On the assumption that the problem occurs at stage one, no volume:

WITH THE UNIT TURNED OFF AND UNPLUGGED!! Open it up:

Check for _any_ mechanical problems. I note there are several PC boards
and quite a bit of point-to-point wiring. On the output driver-to-amp
stage, if there are any broken/shorted connections, this will drive
your amplifier tubes nuts, blue glow, internal meltdown and worse. So
go over this section, all pin connections and board traces with a
magnifying glass, look for carbonization, anything that might indicate
a problem.

Report back.

This appears to be a very nice amp, and reasonably well built (from the
pictures). I certainly do not want to make suggestions that involve
changing or modifying or repairing components without a thorough
physical examination first.

Peter Wieck
Wyncote, PA

[Bob H.]

I assume that auto bias in your amp means they have cathode resistors
in place, no negative voltage supply for the grids of the output tubes,
and no adjustment for bias.

(I have seen old wirewound cathode resistors develope breaks from the
weld points to their leads, and all four of them developing this. It
was a very old amp, however, and not likely here.)

When you say the tubes glow on and off, do you mean the filaments in
the center of the tube, or the plate structure or one of the grid
wires are glowing?

Do all the output tubes glow at once, or are a couple of them glowing?
Do the signal tubes do this as well?

If it's not the filament, but the plates/wires on both channels which
are glowing at an interval, then current through the tubes is greatly
changing, and is common to both channels.

If bias is not a common point to both channels, maybe its a low freq
feedback problem through one of the power supply caps, such as internal
arcing, cold solder joint, dried electrolytic causing a
charge/discharge or ground/unground at low frequency. You could get a
bench cap somewhat close to the cap values, and substitue each ps cap
one at a time to see if the problem stops.

Also, maybe a power supply resistor is arcing internally. I use a
plastic cheap stethescope to listen for this as it usually is audible,
but make sure it is NON CONDUCTIVE. I would imaging a drinking straw
would also work for listening for arcing in resistor bodies.

Also, you can power the amp up on it's side, turn out the lights and
watch it from a safe distance, and watch the underside for any arcing
to ground, etc.

Hope this helps
Bob H.



Dave xxxx wrote:
Bob H. wrote:
Does this amp have fixed bias, coming off of a single bias supply?

Bob H.

its got "auto bias"

[Bob H.]

I reread the original post regarding the popping, and now remember
having a similar sitution, ending up being a component lead being close
enough to the chassis to sometimes arc, and sometimes not. When it did
arc, it played hell with the entire circuit. Also, sometimes a wire's
insulation can degrade with high voltage over time if it's against the
chassis, and eventually will arc through the insulation.

Try to visually localize the popping noise if you can. Be careful of
the voltage present in the amp.

Bob H.

[Keith G]

" Dave xxxx" wrote in message
k...
Keith G wrote:
Absolutely not, Dave's an 'old friend'....

ta old chap I am piggy in the middle

more information

Primaluna Prologue Two amp has gone mental again, i.e. broken down

It's the same problem as before where one or more output valves start
glowing on and off like buggery, loudspeakers drivers being thrown fully
out and back again, loud pops. this is happening with or without music
playing


Dave, Peter's come up with a pretty through investigation procedure and I'm
sure he'd get to the bottom of it, but if I were you I'd just run it in to a
repair tech unless you're confident about fettling it. Contact your seller
first? Also, is there a warranty running on it?

(I've got Phil's Ming Da here and these Chinese amps are pretty well
stuffed - not like a bit of homebrew with plenty of space to play about in!)

[[email protected]]

Keith G wrote:

Dave, Peter's come up with a pretty through investigation procedure and I'm
sure he'd get to the bottom of it, but if I were you I'd just run it in to a
repair tech unless you're confident about fettling it. Contact your seller
first? Also, is there a warranty running on it?

Thanks for the vote of confidence. Like most basic diagnostics, it
takes longer to write it out than to actually do it. I get VERY
squirrelly about visiting suggestions on other's equipment remotely
until I have a very good understanding of both the nature of the beast
and its proper behavior. So it drives me nuts when I am presented with:
"I have this amp, it doesn't work.... Any ideas?

Apologies to Dave are in order and herewith tendered.

Peter Wieck
Wyncote, PA

[Keith G]

wrote in message
oups.com...

Keith G wrote:

Dave, Peter's come up with a pretty through investigation procedure and
I'm
sure he'd get to the bottom of it, but if I were you I'd just run it in
to a
repair tech unless you're confident about fettling it. Contact your
seller
first? Also, is there a warranty running on it?

Thanks for the vote of confidence. Like most basic diagnostics, it
takes longer to write it out than to actually do it. I get VERY
squirrelly about visiting suggestions on other's equipment remotely
until I have a very good understanding of both the nature of the beast
and its proper behavior. So it drives me nuts when I am presented with:
"I have this amp, it doesn't work.... Any ideas?



That will be the 'completist' in you, but no bad thing!

I believe Dave's amp is quite new and almost certainly still in warranty (?)
which is why I suggested he might follow the 'take it back to shop' route.
(Stuffed, it was an eBay Chinese amp, of course!! ;-)

As we are crossposted, let's bring the RATs up to speed on my 2 Chinese 300B
SETs:

Amp No. 2 - little used, perfect behaviour and now gone - snatched away by
an EL34 PP user after he heard it!! (??)

Amp No. 1 - thrashed mercilessly, volume pot went on the fritz (replacement
was promised but never arrived), WW2 Chinese military driver valve fizzing
and had to be replaced, fragile/spindly lead on a (Boer War) German
capacitor broke and has had to be resoldered. Otherwise, still goes like a
train - OK, possibly a bit more Western Pacific than Western Electric, but I
love it and use it all the time!!

:-)