DEAFASABAT
Well-Known Member
Miscue.The meters are a stock Modutect , don't know if there around if there not any VU. Meter that will fit the chassis will work too ,has to be a VU type for proper ballistics
Last edited:
Miscue.The meters are a stock Modutect , don't know if there around if there not any VU. Meter that will fit the chassis will work too ,has to be a VU type for proper ballistics
Hello,
Another question...what is working temperature of this amp? Let say, that its powered up for 4h and have speaker load of 8 ohms and without any input signal? Im asking because both channels warming up same...aprox. 50-60 degree celsious (120-140F). Output DC is 12mV on both channels.
I hope you replaced that melted EVOX cap on the upper left of the bottom pic in post #23.
Did you check with woodyzine. I think that's the name. He has all of Jim Borngiorno's parts and supplies. He lists on eBay.I noticed an occasional "chirp" from one of the channels
Using a signal generator and scope to trace the issue, I found one transistor in the two input differential pairs of (now obsolete) Motorola transistors MPS8099/MPS8599 had been replaced by an incorrect substitute 2N4126.
I need 2 matched pairs of MPS8099/MPS8599 to replace the input differential pairs. Any leads on where I can get these?
Rgds
Mayank
PS The schematic has these as 2N5401/2N5551 which are still available at Mouser, but I believe the MPS pairs were the preferred devices of GAS.
Did you check with woodyzine. I think that's the name. He has all of Jim Borngiorno's parts and supplies. He lists on eBay.
Don't forget SAE Talk on Yahoo groups, and Gasaudio, Mike Bettinger's site, taking the reigns is Kim Lewis.Thanks for the lead. I've just sent him a message.
Looks like you reused old trim pots.It's late ... and tomorrow is a working day, but - I've finally finished the rebuild
The last zip tie is in place neatening the cables between the boards. A few quick pictures from the test bench
View attachment 1497164 View attachment 1497165
More pictures tomorrow along with a complete list of upgrades. I'll be moving this beauty to our main living room setup replacing an Adcom-555.
Rgds
Mayank
Looks like you reused old trim pots.
Why not replace them as part of a full restoration like this?
Good eye!
I actually had ordered multi-turn trim pots from Mouser with the objective of replacing the existing single turn ones (1K for DC Offset, 500 ohms for Bias and VI limiters).
Unfortunately the existing holes spacing was very different and I needed to drill new holes in the PCB.
Fine carbide tip drill bits are on order. In the meantime I am enjoying listening to this very fine amplifier - I am only allowed to put a "black box" in the living room which is all "covered" and has "no wires sticking out"
Rgds
Mayank