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Needing advice on first amp repair
Needing advice on first amp repair
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Old 19th October 2009, 05:31 PM   #1
CharlieM is offline CharlieM  United States
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Location: Savannah, GA
Default Needing advice on first amp repair

Hello all,
I need some advice on a repair. I have no experience repairing electronics myself but Iím fairly handy and my Carver TFM-25 amp needs some work so now is my time to start learning. Iíve heard that electrolytic caps last about 20 years and my amp is a 1990 model so I took the lid off to have a look. The caps looked OK but I found several burned areas on the mother board and there is a Service Bulletin advisory for that in the TFM-25 Manual. Iíve ordered the repair parts and the caps and hopefully I wonít end up with a boat anchor. The view of the motherboard map in the manual is looking thru the board from the component side but I canít see thru the board so I also need a view looking at the trace side to help me find and de-solder the parts. Iím thinking maybe Kinkoís can copy the map onto clear plastic and I can flip it to look at the trace side. Iíve discharged the caps with a lamp so I wonít get fried and Iím making up a checklist so I donít lose my place but before I get started I have some questions:
1) Which is easier: Remove all parts then replace them or R&R parts one-at-a-time?
2) Should I assume new parts are good or do I need to test them before installing?
3) Should I do any testing during the parts replacement process?
4) Do I need to clean and over-coat solder joints and traces after Iím finished? If so,
what are the steps and materials?
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Old 21st January 2010, 02:23 PM   #2
adicio is offline adicio
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I have a similar situation as I recently purchased a Carver TFM-24 amp which is basically the same as the Carver TFM-25 without the analog meters. There is no output from the right channel on my amp 99% of the time. I am going to ask a tech friend to take a look at it. My question is from which supplier did you order your parts? If you could direct me to these suppliers I would be most grateful. By the way is there a site where one can download a free copy of the service manual for the Carver TFM-25 or TFM-24?
Thanks and good look with your project.
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Old 21st January 2010, 04:44 PM   #3
c2cthomas is offline c2cthomas  United States
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Location: Near "Music City" (Nashville Tennessee)
1) IMO R&R all at the same time - it helps keep you focused on the desolder and resolder operations and is quicker time wise as you don't get into start and stop and then restart mode.
2) Always test parts to the best of your ability. If you toss in a few repair parts and one of them is bad it can lead to confusion as well a possible damage to the unit or other parts. BTW - I always go after the power supply 1st - it's pretty hard to get something running unless the PS is working correctly.
3) IF there are in parts of the unit that can be isolated. For example the power supply can usually be isolated and repaired if necessary as a separate unit - then onto preamp - input circuits etc - save the power amp section for last.
4) cleaning and over coating solder joints should be done for ones that inspection reveals need it, or that you suspect need it. Touching up all of the solder joints consumes a great deal of extra time and can create as many problems as it can solve. Excessive heat can be damaging to the PWB and components.

This link might be of some help - Troubleshooting and Repair of Consumer Electronic Equipment
DIY audio can be expensive Ė but getting to see things go up in smoke - that's priceless!!!! ..... "whatever - call it brainfart of Mighty ZM"
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