# Peavey Pacer 100 problem. Can someone assist?



## CountryASS (Nov 14, 2010)

So I had a somewhat working Peavey Pacer 100 and then screwed it up somewhere. Here is what happened.

I plugged the amp into power and plugged in a guitar. The guitar signal came through but was sort of intermittent. It would be quiet and then louder at random times. I then unplugged the power and pulled the chassis out. I looked inside and found that this silver 50u 50v cap was laying inside the chassis. I didn't know where it came from so I proceeded.

After pulling out the chassis, I plugged it in again and found that the amp was still passing sound and wondered where the cap went. I then went and removed all the screws that held the circuit board in and went to pull it out. As it turns out I didn't unplug the power and as I pulled the board out something on the board touched the chassis and it sparked. I realized that the power was plugged in, unplugged the power and continued to remove the board. I looked online and found out where the loose cap went, I then re-installed the loose cap and re-installed the board.

http://img4.imageshack.us/img4/994/wideloosecap.jpg

When I plugged in the power and turned it on, the resistor (pointed at with the pencil)









started to smoke. The sound out of the speaker was a loud hum like a bad power cap. Does it have something to do with the power cap?









What is making the resistor burn out?


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## Wild Bill (May 3, 2006)

CA, that 50/50volt cap is called an electrolytic cap. They are polarized, which means that one side should be at DC+ and the other at DC-, which is usually (but not always!) ground. Looking at the picture it appears backwards to the other one. A picture doesn't tell you if that is correct, of course. It doesn't show you the wiring - you need the schematic for that. Still, if you look at the traces at the bottom of the board you might see if the negative side of the two caps is connected together. That would confirm you've got the second cap in backwards.

When electrolytic caps are connected backwards they tend to bulge and eventually explode! Makes a helluva mess! Scary bang, too!

Best to change out that resistor as well. It probably has been damaged feeding a backwards electrolytic cap, which would have been like feeding into a dead short. If that cap was NOT backwards then check back in and we'll keep trying!

WB


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## bcjek (Oct 29, 2010)

I have a schematic for that amp [as well as the amp itself]. 

You can get it online here: Click Here

Michael


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## bcjek (Oct 29, 2010)

All electrolytic capacitors have a limited life span. This occurs because the electrolyte in the element eventually dissipates, and I think that all of yours need replacement. Your amp dates from early 1975 [as per the transformer codes].



The changes in performance over time can be described as follows:
(1) Eventually, the capacitance begins to drop off.
(2) Generally, when voltages are applied, the leakage current begins to drop.
(3) Finally, at the end of the life span, the capacitor enters an open-circuit mode as the dielectric dries up.


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## CountryASS (Nov 14, 2010)

*But......*

Thanks for replying everyone. I agree that the caps should be replaced but I don't know why that resistor is burning out. Can a bad cap burn out a resistor? I have the schematic. Where can I meter to find out what is running to hot?


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## Wild Bill (May 3, 2006)

CountryASS said:


> Thanks for replying everyone. I agree that the caps should be replaced but I don't know why that resistor is burning out. Can a bad cap burn out a resistor? I have the schematic. Where can I meter to find out what is running to hot?


Absolutely a bad cap can burn out a resistor! Or, an electrolytic cap put in backwards would look like a dead short to the power supply and burn out a resistor! That's why I suggested you check out if the cap is in the right way around.

WB


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## Wild Bill (May 3, 2006)

CountryASS said:


> Thanks for replying everyone. I agree that the caps should be replaced but I don't know why that resistor is burning out. Can a bad cap burn out a resistor? I have the schematic. Where can I meter to find out what is running to hot?


Just checked out the schematic. No offense, but I think you are in over your head! You need a tech, I'm afraid. You may well have had an output transistor short, which may have taken out something else as well. That could also explain the resistor burnout.

At this point things are getting too complicated to try to walk you through troubleshooting like some kind of remote-controlled robot. It's like trying to help someone with no automotive mechanical knowledge take his engine apart through emails! It's a LOOOONNNNGGGG process!

Perhaps some of the other guys may want to chip in a bit more but at this point I'm afraid I'm going to have to bail out. At my age I don't know if I have that kind of time left!

WB


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## CountryASS (Nov 14, 2010)

So I finally fixed the Pacer. Here is what I did. After reading a bunch of stuff online about what the problems could be, I replaced the caps with Radio Shack caps. The original caps were bursting. I replaced the output transistors with Radio Shack 2N3055 transistors and after metering the 5W resistors I found one of the .47ohm resistors was bad and replaced it with a Radio Shack wire resistor of the same rating. It now sounds really good and has some great punch. About $15 in parts and it is back in action. Thanks to all who added comments and advise. I really appreciate it. Hope we do it again sometime. Thanks again.


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