Found a 1962 Gibson GA-79RVT

[rake411]

A young guy at work told me his dad had an old Gibson amp in the attic that hadn't worked in years and almost
caught on fire last time it was plugged in. When he described it and said it was kind of wedge shaped I tried to
act disinterested.

A couple weeks later I bought it for $100

The upper 200Ω 10W resistor and 25µF capacitor were burnt to ash and the power supply choke smoked.
I replaced those parts and totally rebuilt and rewired the power supply.
Next power up the resistor burnt and the new cap exploded.

THEN I realized the 7199 phase inverter tube had been replaced with a 12AX7 with no rewiring of the tube
socket. Bought a 7199 tube and all or the other eight tubes and the next power up was much more successful
but a lot of loud hum.

More investigation showed the earlier tech had replaced the original 20/20µ 450V audio cap with a single
40µF cap and combined the circuits. I replaced that with two new 20µF 450V caps on separate circuits.

22 days after purchase and $380 in parts later I have a vintage tube amp that sounds like a 1960s amp
is supposed to with no noticeable background hum buzz or hiss.

This could be my highest profit turnover ever.
I don't see that happening.
Being they only made about 1132 of this model I'm thinking this one is keeper

Picture red arrows point out the bad or failing parts. Other picture is the repaired chassis.
I think I'll leave the tolex and grill cloth just as it it.
I'm two years older than this amp and that look just fits me!

[mozz]

How did you spend $380 in parts? Seems high, Unless you had a choke professionally wound to original specs.

[g1]

He mentioned a re-tube. Maybe NOS?

[rake411]

Tubes were the majority of cost.
The 7199 was a little over $70 and the the three 6EU7s totaled $77
It does add up quickly.

[mozz]

Wow. Last 7199 i bought 2 years ago was $20, RCA brand new in the box. 6eu7 not sure on the price. You could have bought the 6gh8 adapter and rewired the 6eu7 for 12ax7. Does that model have the field coil speaker? I had a GA75 way back when.

[pdf64]

Great find and well done!
I’m perplexed why a light bulb limiter wasn’t used to bring fault current down to safe levels when powering it up, especially when warned it smoked the last time it was used?

[rake411]

Wow. Last 7199 i bought 2 years ago was $20, RCA brand new in the box. 6eu7 not sure on the price. You could have bought the 6gh8 adapter and rewired the 6eu7 for 12ax7. Does that model have the field coil speaker? I had a GA75 way back when.

Wish I could fine them for that price.
I did consider the 6gh8 adapter but wanted to keep is as original as possible.

[rake411]

Great find and well done!
I’m perplexed why a light bulb limiter wasn’t used to bring fault current down to safe levels when powering it up, especially when warned it smoked the last time it was used?

Certainly should have but didn't.

Several years ago I refurbished a 1978 Fender Deluxe Reverb. Smoked components in it too on first power up.

I'm thinking a Variac may be added to my bench if I find another project.

[pdf64]

My variac is a little used boat anchor, whereas my light bulb limiter ranks about#2 item of useful things. Not up there with a multimeter, but in terms of earning its keep / bench space / avoiding magic smoke release, to not have one seems remiss.

[rake411]

I had built one many years ago. No idea what ever happened to it.
Maybe time to build a new one.

I do get lax sometimes.
Just like I'm constantly preaching the hazards filter caps, yet I still get the occasional knuckle numbing myself
from not discharging the caps.

I know better.

[nevetslab]

A young guy at work told me his dad had an old Gibson amp in the attic that hadn't worked in years and almost
caught on fire last time it was plugged in. When he described it and said it was kind of wedge shaped I tried to
act disinterested.

A couple weeks later I bought it for $100

Picture red arrows point out the bad or failing parts. Other picture is the repaired chassis.
I think I'll leave the tolex and grill cloth just as it it.
I'm two years older than this amp and that look just fits me!

I remember this amp, having seen one at Saul Benton's shop in Hollywood back in the mid-60's. Back in the era of Gibson's Titan and Mercury series amp/cabinets, and around when the Firebird and Thuderbird came out. Very cool amp.