Very old pignose 7-100

[Enzo]

Does the noise seem to relate to using the pot? Or did you just clean it for old times' sake? If the pot makes noise, it can be other things than needing cleaning. The pot can be worn out or have cracked solder, so motion triggers noise. Also, if a pot has DC voltage across it, it will be noisy when moved.

Does tapping the amp make noises? That would be a loose connection somewhere. Don;t be shy, give it a solid swat on top.

If it just sits there alone making pops and crackles and grumbling noises, my first suspect is a noisy transistor.

[angelodp]

just sitting there

Hi Enzo, just just sitting there its constantly crackling and popping. I do get a signal and can hear the guitar ok. The Pot simply makes it all louder. I reflowed all the solder joints, still there? How do i trouble shoot further please. Looks like its 2SB56 germanium Transistors.

Best A

Does the noise seem to relate to using the pot? Or did you just clean it for old times' sake? If the pot makes noise, it can be other things than needing cleaning. The pot can be worn out or have cracked solder, so motion triggers noise. Also, if a pot has DC voltage across it, it will be noisy when moved.

Does tapping the amp make noises? That would be a loose connection somewhere. Don;t be shy, give it a solid swat on top.

If it just sits there alone making pops and crackles and grumbling noises, my first suspect is a noisy transistor.

[Enzo]

Isolate the problem. Can you turn the volume control to zero and kill the noise?

I'd use a scope or a signal tracer (google that) to follow the signal path through teh amp. It is only two transistors in the preamp, and a pair in the power amp.

I'd try grounding the signal path. There is DC on the transistors so don;t ground it directly, but a large cap like a 0.1uf clipped to ground then touched to circuit points will serve to shunt off a lot of the signal. SO if grounding the base of the first transistor with a cap diminishes the noise, or muffles it, then we know the noise was coming in there, and if that has no effect, then the noise is later in the circuit. SO we do the ame thing at the base of the second transistor. Or at the collector of each. Step through the circuit this way to find at what point the noise enteres.

Other techniques would be to hit parts with freeze spray to see if the thermal shock affects the noise. Or heat.

[angelodp]

Ok great. Are replacement Transistors readily available? Which leg is the base of the transistor please. Tried it with a .22uf cap and it just made a loud buzz on the transistor legs?? No shunting of noise ( crackle pop ). BTW vol to zero kills noise.

[Enzo]

All the 7-100 circuits I know have the volume control before the entire circuit. So if the thing kills the noise, it wouldn;t be coming from the circuitry. I'd make sure the input jack is snug and its contacts clean.

How about this: turning the volume to zero kills the noise, OK, now plug a guitar into the input jack and turn the volume control on the guitar itself to zero, but leave the control on the amp up. Does THAT kill the noise? I am wwondering if the grounding contact on the empty jack is making noises.

[Enzo]

Oh, yes, suitable transistors are certainly available. As to which leg is which, I have no idea what transistors you have in there.

[angelodp]

still there

ok here is a ne twist. With the guitar volume full up the amp volume pot seems to generate less noise at it reaches full rotation. So it progressively gets more scratchy as you turn the amp volume pot up and then at the very end of travel of the amp pot it dies back a bit but still scratchy??

With the guitar volume all the way down and the amp volume up it still makes noise.

Wait a minute..... Enzo I think I found the culprit. The # 3 leg of the amp vol pot ( that goes to the signal on the jack ) that tab was cracked.... so poor connection. I am cleaning up the pot and will re-insatll with fresh connections soon.

Best A

NOPE.... still very scratchy and I do think this pot is a gonner. Any idea where I can get a similar 39D PC65- 10KA made i n japan has the on/off

All the 7-100 circuits I know have the volume control before the entire circuit. So if the thing kills the noise, it wouldn;t be coming from the circuitry. I'd make sure the input jack is snug and its contacts clean.

How about this: turning the volume to zero kills the noise, OK, now plug a guitar into the input jack and turn the volume control on the guitar itself to zero, but leave the control on the amp up. Does THAT kill the noise? I am wwondering if the grounding contact on the empty jack is making noises.

[angelodp]

I took the pot out and went threw it carefully and its fine and working. I did realize ( thanks to Howard at Pignose ) that the transistors that are most at risk are in the little round heat sinks that are attached to the transformer cover and Enzo you were quite correct they are B324 ( SB324 ). I found a couple on ebay for $5 and waiting to throw them in and see. Howard indicates that these two T's are the most often seen part failure, albeit rare. Will report back soon and thanks for the help.

[angelodp]

Ok got it going again. It turns out that it was not the transistors in the heat sinks. I got two replacement 2sb32's and the problem persisted. I tried the coolant from an air can on the other two transistors and the 2SB54 diminished in noise when sprayed. I compared the specs for 2sb32 and 2sb54 and they were so close that I decide to pop in the sb32 into that slot that was helped by the coolant..... presto.... pignose back to its old self. The upside down air can trick seems to be quite useful in zeroing in on the bad component.

Thanks

[catnine]

I know this thread is old however.

I am a bit confused . I contacted Pignose today and asked a few questions and got the schematic emailed to me. Mine has a white lable with a 95/and 4 digits following the / Also the lable reads 7-100 R . I asked about the R and was told it stands for restart , they stopped making the amps in 1984 and started again in 1985 . I also called to ask about what the speaker OHM was and was told it was 4 OHM then I got the schematic and it shows 8 ohms so I emailed back and was told sorry it is 8 ohms. I also asked about the eletrolyic caps , as you know in tube amps they need to be changed but since the 7-100 is SS and low voltage they will last forever. they never had an issue with them to date.

I am confused about the speaker OHM rating and the only way to tell I suppose is to un-solder one wire off the speaker and check it. It really doesn't matter all that much since my 7-100 works just fine and I don't need to change the speaker . I do know in the Pignose Hog 20 the speaker was 4 ohms because the amp new had a noise and I thought it was the pignose emblem on the grill because it was loose , I made certain it was tight and still had the nosie so they sent me a new speaker and that was 4 ohms. Different amp though. They haven't made the 7-100 in the US since 1984 .

[JHow]

...I also asked about the eletrolyic caps , as you know in tube amps they need to be changed but since the 7-100 is SS and low voltage they will last forever. they never had an issue with them to date...

I have many transistor radios in which the only thing wrong with them was the e-caps. Time catches up with everything (everyone), although I'd like to think things from 1984 are still "new"...

[catnine]

I took the pig's chassis out about a year ago and all the e-caps looked fine , none leaking. The way I look at it is there are very old guitar pedals out there and I have old radios and boom boxes that never had any issues and still work. Besides that most are powered by 6 to 9 VDC and all have e-caps rated much higher than that. Now when you get into a tube powered amp then you have much higher voltages and heat going on.

I mean if something blows it blows and then I'll repair it. The people at pignose did say they never had an issue with the e-caps . I can't even say I have heard of replacing the e-caps in a 120VAC powered amp not that I known much about them other than I don't like the sound they offer up. I did try a few like the 1994 fender bronco that was touted as sounding like a tube amp or the Vox small SS amps and a danelectro nifty fifty. I guess the SS fender bronco came about as close as one can get at the time.

[Bobdudeman]

Hi, I know this is an older post, but I would like my pignose to run an extension cab as well. Can you please explain this procedure you did. What kind of wire? Thank you

[ReginaldBisquet]

Rather than start a new thread, I thought I would come back to this one and post.

I recently bought a circa 1980 Pignose 7-100. Here's what the circuit board looks like:



All resistors 1/2 watt. 5% tolerances.

1 - 68k ohm
2 - 47 ohm
3 - 4.7k ohm
4 - 220 ohm
5 - 510 ohm
6 - 470k ohm
7 - 10v 47uf
8 - B175B (98) NPN transistor (~ 16V)
9 - 39k ohm
10 - 16v 10uf
11 - 16v 10uf
12 - 4.7k ohm
13 - 15k ohm
14 - B172A (90) PNP transistor (~ 16V)
15 - 10v 100uf
16 - 6.8k ohm
17 - 220 ohm
18 - 10v 100uf
19 - 100uf tantalum capacitor
20 - 220 ohm
21 - 1 ohm (1 watt)

Preamp output has a 33k 1/2 watt carbon resistor.
Input jack has a Z5F, .001k 1kv capacitor.
Potentiometer also has a Z5F, .001k 1kv capacitor.
Potentiometer made by ALPS (Japan). 10k ohm (audio).

I'll have details on the pre and output transformers later this month.

[bigdaddydiesel]

Hello, realize this is a bit of a necro post but this is a thread that has good resources. I have an old Pignose 7-100 with original germanium transistors. Currently the amp only produces hum that doesn't grow in volume or decrease once the on/off volume knob is turned. At the highest volume with a guitar plugged in I get a low, fuzzy signal with a nasty octave effect. Anybody have an idea what might be the problem? I'm suspecting it's a transistor issue, however following angelodp's post earlier in this thread regarding "Howard from Pignose" claiming the power transistors mounted to the heat sink usually go first, it may also be one or both of the SB324H power transistors? I've already hit them all with freeze spray and the issue didn't change. I also poked around with a chopstick to find bad solder joints but didn't find anything.

I would like to get this amp up and running and keep my trigger finger from getting replacement transistors before I have a good idea. Thank you!