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Topic: Repairing intermittents on Session 500 |
Lynn Kasdorf
From:
Waterford Virginia, USA
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Posted 17 Aug 2000 9:31 am |
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I have this old Session 500 that works every now and then. Usually however, there is some combination of (1) no sound at all, (2) very distorted sound, (3) the yellow overload lamp on. It comes and goes. I think I have been able to slap it back into submission with percussive maintenance a few times.
I have not used it for a few years becasue of this.
I have had it on the bench a couple times and went through every damn molex connector and cleaned and tightened the pins. I have resoldered where the molex pins attach to the PCB.
It always works on the bench! I put it back together and it usually fails quickly or the next day.
I have thought about eliminating the connectors and soldering the wires directly. This would make future disassembly a pain.
Ideas? I can't be the only person who has had problems with Peaveys like this. |
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Blake Hawkins
From:
Florida
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Posted 17 Aug 2000 9:50 am
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Lynn, Sounds like you've pretty well eliminated the connectors as the problem.
Have you tried powering it up while on the bench and tapping the board?
I use a wooden pencil with a rubber eraser for this.
Putting a little stress on the board sometimes helps.
I'd check all the component solder connections associated with the power supply too.
There is a possibility it could be thermal related. A little gentle warming with a hair dryer while it is on the bench could help spot the bad connection.
Also going over the solder side of the board with a strong magnifying glass could help pinpoint a bad connection.( I look for dull joints and cracks in the solder.)
You could als "shotgun" the solder joints...that is re heat every one on the board.
Blake |
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Curry Coster
From:
Glen Burnie, MD USA
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Posted 17 Aug 2000 9:50 am
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Lynn,
I had a Session 500 that was doing that. I put it the shop and they replaced the input jack. Sounds crazy I know but it fixed it. Try it and see.
Hope I helped.
Curry |
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Jack Stoner
From:
Kansas City, MO
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Posted 17 Aug 2000 10:44 am
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I'd be willing to bet it's the filter capacitors in the power supply. My old Session 500 acted almost exactly like that and it turned out to be the filter capacitors in the power supply for the + and - 52V that feeds the output transistors. It drove me crazy til I found it as there was only about a 2V drop from what it was supposed to be.
The Caps are 5000uf at 55V. You should be able to get them from Peavey. I'd also replace the + and - 15V filter caps while your at it. They are 1000uf at 35V. |
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Lefty
From:
Grayson, Ga.
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Posted 17 Aug 2000 2:38 pm
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| Thanks Jack. I will file this with paperwork for my session 500. So far, my has performed flawlessly, knock on wood. |
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Lynn Kasdorf
From:
Waterford Virginia, USA
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Posted 18 Aug 2000 12:53 pm
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| Thanks for the replies, all. I'll try some of the things you guys suggest. It is a cool amp, when it works! |
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Dennis Detweiler
From:
Solon, Iowa, US
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Posted 18 Aug 2000 5:06 pm
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Another possiblility...the power transistors are usually pushed into a pin jack type of receptical. sometimes they will get loose and require crimping to tighten them. Last resort easy fix.
Dennis |
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Lynn Kasdorf
From:
Waterford Virginia, USA
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Posted 19 Aug 2000 5:46 pm
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| The world wwould be a much better place if there were no connectors... |
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Bob Metzger
From:
Waltham (Boston), MA, USA
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Posted 20 Aug 2000 11:33 am
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...percussive maintence.... sounds great to me!
Although these may not fall into your symptom category, I would try re-crimping the internal fuse holders for the +/- 15 volt supply. I add a little dot of clear nail polish to insure that the fuses don't move when the metal seems a bit fatigued and loses its resiliency. Also, check all jacks that have switches and make sure the swiches are closing when they're suppose to be closed and opening when they're supposed to be open. Use your voltmeter to carefully check for proper voltages as per the schematic. Solid state amps accomplish most of it's work in the power supply and output stage and this is the best place to spend your time.
Bob |
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gary darr
From:
Somewhere out in Texas
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Posted 20 Aug 2000 1:25 pm
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| I too had a similar problem with my 500, what I didnt realize was when I had everything tore apart to check the molex's I had pulled the connections to the speaker partly lose from the terminals on the speakers . I dont know if this is your problem but is worth a look. lots of luck! By the way I to have been guilty of percussive maintenance !!!!! [This message was edited by gary darr on 20 August 2000 at 02:30 PM.] |
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Bill Crook
From:
Goodlettsville, TN , Spending my kid's inheritance
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Posted 21 Aug 2000 5:17 am
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| When you put it on the bench, leave it there a few days, then come back and check it again. I bet it will have the problem. I think what you will find is a cold solder joint somewhere. After a day or two, the cold solder joint oxcidizeds (sp?) over again and problem shows up. Usually the bad joint will be in a region where heat is generated, like a large resistor, or other current sinking device. These problems are hard to find. |
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Bill Ferguson
From:
Milton, FL USA
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Posted 21 Aug 2000 9:53 am
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When all else fails, send the chassis to Peavey and let them go through it and bring the entire unit back up to specs.
They work cheap.
Bill |
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