Question about Music
Intermittent problems like this are hard for the shops to find... the thing will sit for weeks and work while on the bench.
This does have a tube in it, and I am sure that has been replaced, but that is the first thing to replace as the heater in them can break mechanically and come on and off causing intermittent operation.
The next thing is a visual inspection. It takes a trained eye to spot things like cracked circuit boards, broken leads into vilume control pots, and bad solder joints.
You have spent too much so far so this is what I recommend for you to try... It is DIY. Remove the amplifier and take a small soldering iron and some electronic solder (rosin core) and resolder EVERY connection on the board. Trying to have you check the joints is hard to describe other than looking for a tiny grey line on the meniscus of the solder fillets.
Next, get a very bright small LED flashlight and light the backside of the board looking for cracks. Look especially near mounting points of the board AND heavy components like electrolytic canned capacitors.
Look for resitors or components that might be cracked.
Look for areas where the board seems to have heat discoloration marks.
Look for connector problems. The input jacks and the soldering around them are often a problem. Jacks that have switches that allow preamp and access to the power amp OFTEN have poor contacts on the switches that oxidize or get loose.
Remember the vacum tube portion of this runs at high voltage so unplug the unit for a bit before working on it.
lastly, with the unit operating, take an insulated stick and do some poking of components and putting pressure on the circuit board. This looks for marginal component connections and cracks in the circuit traces... one listens for the least scratchy noise in the sound... you dont need audio going through for this test.
Posted on Sep 10, 2010
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Posted on Jan 02, 2017
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