Hello all hope everyone is doing well and remaining warm.
My amp is an Adcom GFA 555 mk1.
I have read in several places now that aging transistor drivers can wipe out our inline speakers. I'm making some time to refresh those and maybe whatever else would be adviseable while im in there, hence this post. Im trying to remain as economical as possible(on a budget) and focusing on making sure those drivers dont burn out as well as upgrading what is absolutely likely to have degraded and may be affecting sound quality. I will be doing a thorough refresh all sourced from Hoppe, his designs are the inspiration in this 'safety refresh'.
I will be opening up the amp to both test as many components as possible while I address the input board at the same time. The amp is working fine. I do not expect to discover filter caps or other caps as bad. But one can never know what you might find when you start taking measurements so whatever I find is truly out of wack from specs I will order and replace. Please offer advice on components that shouldnt be skipped out on due to age or to assure sound clarity or if you see anything listed as a mistake. So far I have come up with the below to be replaced for certain:
The main culprits of disasters;
(T0126 transistors):
Q7s,Q6s = will recieve KSA1381ESTU
Q4s = will receive KSC3503DS
Both Q7s and Q4s will also receive heatsinks. Q6s do not necessitate.
(T092 transistors):
Q1s and Q2s = will receive Hoppes matched pairs KSC1845FTA
(TO220 transistors) for the Output boards: Please which paste and which thermistor(1)?
Q11s = will receive MJE15033G
Q12s = will receive MJE15032G
.1% Precision resistors in the input path for gain precision:
R1s,R5s = will receive RN55E1001BB14(1k ohm)
R2s,R6s,R223 = will receive RN55C2212BRE6 (22k1 ohm)
I feel the above will limp me by for awhile until a full complete Hoppe overhaul in near future. Obviously any components found out of wack will require another parts order.
Please let me know if there are specific caps or anything else that you think is absolutely indispensable must do's while I am in there. With a little luck I'll go in do these upgrades and come out without needing anything else additonal. Fingers crossed. I know some people swear you must do filter caps but if they are not out of wack specwise I think I will leave them in place unless its factual that simply their age effects sound? I will be adjusting bias before I bottle her back up as per Adcom manual.
I was also considering the adjustment pots. Please advise if og are really that bad.
Thank you for your time.
This amp drives fully restored to original specs Polk M10s.
My amp is an Adcom GFA 555 mk1.
I have read in several places now that aging transistor drivers can wipe out our inline speakers. I'm making some time to refresh those and maybe whatever else would be adviseable while im in there, hence this post. Im trying to remain as economical as possible(on a budget) and focusing on making sure those drivers dont burn out as well as upgrading what is absolutely likely to have degraded and may be affecting sound quality. I will be doing a thorough refresh all sourced from Hoppe, his designs are the inspiration in this 'safety refresh'.
I will be opening up the amp to both test as many components as possible while I address the input board at the same time. The amp is working fine. I do not expect to discover filter caps or other caps as bad. But one can never know what you might find when you start taking measurements so whatever I find is truly out of wack from specs I will order and replace. Please offer advice on components that shouldnt be skipped out on due to age or to assure sound clarity or if you see anything listed as a mistake. So far I have come up with the below to be replaced for certain:
The main culprits of disasters;
(T0126 transistors):
Q7s,Q6s = will recieve KSA1381ESTU
Q4s = will receive KSC3503DS
Both Q7s and Q4s will also receive heatsinks. Q6s do not necessitate.
(T092 transistors):
Q1s and Q2s = will receive Hoppes matched pairs KSC1845FTA
(TO220 transistors) for the Output boards: Please which paste and which thermistor(1)?
Q11s = will receive MJE15033G
Q12s = will receive MJE15032G
.1% Precision resistors in the input path for gain precision:
R1s,R5s = will receive RN55E1001BB14(1k ohm)
R2s,R6s,R223 = will receive RN55C2212BRE6 (22k1 ohm)
I feel the above will limp me by for awhile until a full complete Hoppe overhaul in near future. Obviously any components found out of wack will require another parts order.
Please let me know if there are specific caps or anything else that you think is absolutely indispensable must do's while I am in there. With a little luck I'll go in do these upgrades and come out without needing anything else additonal. Fingers crossed. I know some people swear you must do filter caps but if they are not out of wack specwise I think I will leave them in place unless its factual that simply their age effects sound? I will be adjusting bias before I bottle her back up as per Adcom manual.
I was also considering the adjustment pots. Please advise if og are really that bad.
Thank you for your time.
This amp drives fully restored to original specs Polk M10s.