another punch 100 dsm issue

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If C9 isn't shorted and none of the FETs in the power supply are running hot, it's probably normal. They use a large resistor so it can dissipate the heat produced by normal operation. Unless it's getting hot enough to desolder itself, it should be OK.

For the gain problem, check the signal on pin 2 of both driver boards. I think both should have essentially no signal. If one does, the 10uf capacitor may be defective. Many of these caps leaked and caused damage to the board. To see it, you generally have to lift the capacitor.
 
On pins 17 and 18 of the input board do you have the same signal level?

If you don't have a scope, use a test tone and measure the voltage with your meter (set to AC volts).

You stated that the gains were down in both channels. Do you mean the gain control is set to a low level or that there was insufficient gain (less than you'd expect) in both channels?

The 540s won't have any effect on the gain.
 
You seem to have some more defective capacitors. C102, 103, 202 and 203 (guessing 202 and 203, they're not shown on the schematic) are the ones you need to check. Each cap should have the same voltage on each of its terminals. If it has 0v AC on one terminal, it should have 0v AC on the other terminal. If it has 0.5v AC on one terminal, it should have 0.5v AC on the other terminal.
 
Resistor values for Punch 100??

Followed this thread because it is similar to the issue I am having with my Punch 100 DSM. In short R2, R17 and R231 are running very hot. (Interesting side note, R131 is the identical resistor to R231 on the right channel and it is running very cool.)

It appears that both R2 and R17 may have already failed. R2 returns an open short (infinity) when tested with a multimeter. I cannot read the banding because it has faded due to excessive heat. I can only make out Digit 1 and Multiplier values which appear to be Brown and Gold respectively.

R17 returns a value of 6.2K ohm when tested with the multimeter. This does not seem right because the banding is Brown, Black, Black, Gold, which suggests a 10ohm.

R231 tests OK, but is running quite hot compared to R131. This is a 220 ohm resistor.

Can anyone tell me what the values for R2 and R17 should be so I can replace them?

Without any speakers conntected to the amp or load of any sort, currently it turns on momentarily (with a very dim remote LED light) and trips my power supply's protection circuit within 10 seconds. The PS is rated for 3amp draw.

Any insights or shared schematics would be greatly appreciated. This amp has been great to me for over 15 years and I would love to resurrect it! Thanks in advance!
 
Gettin' there

Replaced R2 and R17 - amp is stable and no longer tripping circuit breaker.

R231 is still hot but checking OK when tested.

Tested DC voltage across left channel output and receiving 30 volts. Right channel has no DC reading.

I'm pretty certain Q206 and Q207 have failed. Receiving a short when tested. Q203 and Q204 are testing OK.

I suspect the next step is to replace the FETs and retest.

Have I missed anything? And is there anything I should keep in mind when replacing them? Thx.
 
I undertstood you to mean Leg 1 as being the Gate of the FET and Leg 2 to be the Drain.

When tested, Q207 is 33.3 ohm, Q206 is 13.2 ohm

Just for kicks, I tested the resistance between the Drain and Source, and they both return 12.2 ohms.

I'll remove Q206 and test for DC.
 
Perry,
Ran into a snag. Pulled Q206. Didn't get a chance to check for DC because when I went to bench test the power supply began tripping again? Tested it several times and each time R17 is red hot, to the point that I saw smoke from it just before the breaker tripped. The resistor is still checking out OK tho.

So, I took readings on all of the Power Supply FET's and I will forward the results to your private address. Sigh. Thx.
 
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