Fisher 400 Right channel out

[Planedoc]

I have a Fisher 400 amp that has a non working right channel. It DOES work though the headphone jack though. Any tips on where to start in my troubleshooting? What are the troubleshooting implications of having both channels in headphone but not speaker?

The full story: Got it in working unrestored condition with what looked like original power tubes. Used it as is for a month or two and the right set of power tubes failed with me standing right there. I saw purple sparks in one power tube and heard loud static (the unit had just been turned on so no music was playing). Turned off quickly.

Replace all 4 power tubes with new old stock, did the selenium bridge replacement and changed the large paper cap. inside.

Upon testing the amp on the aux input with mp3 player, the right channel was bad. changed the input to the tape, and both channels worked. Used the amp that way for a couple of weeks, and now the right channel is bad on all outputs, and the FM radio. Again though, i DO have both channels though the headphone jack.

Fairly early model - 24000 serial range

Thanks in advance!!!

 

[AlTinkster92]

Welcome to AK first of all, no expert here but sounds like this receiver needs attention. Have you cleaned the controls with Deoxit? Reason I ask is that you get both channels on tape so I would start there. Let the Forum know......

 

[Planedoc]

Ugh. Disregard - bad speaker wire. I fooled myself when checking that I guess.

 

[larryderouin]

I would still update it, as everything is pretty well tired or shot. As is it won't last long without problems. Nip them in the bud. Start with(New Can caps and new coupling caps in all stages), 100Ω 1/4w Screen stability resistor upgrade (helps prevent tube arcing), 10Ω cathode resistors (fusing and allows you to determine tube load in ma.), at least a 10KΩ pot in the bias supply circuit (to allow output tubes to NOT be overloaded) if not individual bias adjustment control, but 1st you need to clean ALL controls with CAIG DeOxit (D-5 or DN-5) and follow that up with Faderlube (F-5). Plenty of upgrade threads for the 400 here. Everything has been tested, and proven viable. Dave Gillespie's threads for upgrading the 400 are considered Gold or Holy Grail (depending on your outlook). Plenty of guys here who have done multiple 400's and can give you guidance on upgrading it if you feel it's out of your comfort zone, or cash strapped and want to do it in stages.

For cleaning controls, read this thread for starters, "The idiots Guide to using De-Oxit (Re-visited)" Then hit ALL Controls. If it goes in-out, up-Down or Round & round, it gets DeOxit.