Questions about a Fisher Console restoration

[grindfix]

Wow and thanks. Best place to purchase parts? Mouser?

Have you tried to run it?
Did you take any measurements?
What kind of DC and Bias (Idle current) reading did you get?
Pardon if you are familiar with the following.
I wouldn't just start replacing (most likely needed) capacitors without knowing if your output transistors, bias networks and all other circuitry is good. DBT is a good test instrument that will tell you if there is a short by glowing almost full brightness. 100-120W bulb should be good. Incandescent only. Bulb should light-up briefly and dim-down. That would be a good sign. It will glow brighter with the signal present. Higher volume = brighter glow. Using variac together with DBT is even better. This would allow you to gradually increase voltage while watching bulb glow as power supply capacitors take their charge. Bias reading will be lower with DBT inline. Please share your progress and good luck!

 

[PJP122954]

I found the files. They are actually for a 59A from a 65 Ambassador. NO PROBLEM. The 59A adds 4 transistors to the total for 8, vs. 4 on the 49A. Parts are generally the same value and voltage. Parts are in the same location. Parts that are on the overlay, but not on your 49A (Mainly on and surrounding the outer transistors in both rows) disregard. 1st is the capacitor overlay, 2nd overall resistor overlay, 3rd is closeup of the output transistor section.
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Hey Larry....do I need to replace all the caps and resistors that are circled on the 59A overlay or just the ones that arrows are pointing to? I'm new at this and want to do it correctly. I also just picked up a 690A/690T combo. Thanks for all your help!

 

[larryderouin]

You should at one time or down the road you'll be in it again. Plus the aggravation of having to figure out what to get and paying shipping twice. Resistors check unless it's one of the green ones. I'd bump up the 1.2KΩ 7W to 10W and the 390Ω 3w to 5W each. They'll still run hot (normal) but they won't be running close to limits.

Honestly I can't remember why he arrowed the 4 resistors(?). They might be the bias diodes if the pots (4 of them in the Solid State section) are gutted. How about some pics of your amp from underneath.

 

[larryderouin]

OK. It looks like Your's doesn't have the Arrowed parts. It has the BIAS "upgrade" from the factory or a dealer installed it. Check all the resistors with a meter for value and replace if more than 5% off spec. I don't think you'll have that many, if any to replace. FISHER used top line resistors and they rarely go bad that I've seen. The caps are a different story however. They were usually top shelf stuff when new but as with anything that carries water (electrolytics) they eventually dry out.

If it's an ERO-FOL, generally they stay good (sealed PIO's or Film). The dipped caps (brown kidney shaped or "dog turds") should be replaced as they get electrically leaky.

 

[PJP122954]

OK. It looks like Your's doesn't have the Arrowed parts. It has the BIAS "upgrade" from the factory or a dealer installed it. Check all the resistors with a meter for value and replace if more than 5% off spec. I don't think you'll have that many, if any to replace. FISHER used top line resistors and they rarely go bad that I've seen. The caps are a different story however. They were usually top shelf stuff when new but as with anything that carries water (electrolytics) they eventually dry out.

If it's an ERO-FOL, generally they stay good (sealed PIO's or Film). The dipped caps (brown kidney shaped or "dog turds") should be replaced as they get electrically leaky.

Thanks Larry...you expert advice is always appreciated. I assume my 690A will be essentially the same deal.

 

[larryderouin]

Pretty much. The 59A is essentially an updated 690A. Parts lists between the two should be pretty much equivalent, at least that's what i remember.

 

[larryderouin]

I found the thread that the drawings on post # 16 came from. https://audiokarma.org/forums/index...ance-1965-fisher-ambassador-vii-a-690.684947/ It's on a 65 Ambassador