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Adcom GFA-5800 Cap replacement
Adcom GFA-5800 Cap replacement
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Old 16th November 2021, 01:40 AM   #1
exojam is offline exojam  United States
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Default Adcom GFA-5800 Cap replacement

I am placing this here since it seems like as good as place as any, especially since Mr. Pass designed it.

I was wondering if anyone has done a full cap replacement on this unit recently and if so would you have a copy of what the cap part numbers that were used are.

I have not had a chance to break open the unit since I picked it up. Not only that, but I purchased it from a gentleman who babied all of his gear but do to the age of the unit I would have to believe the caps could stand to be changed out.

I was also wondering if folks who would replace the caps if you would also replace some of the transistors, like the 2SC3298B (this would be discontinued, so I would need to find a suitable replacement).

Thanks in advance.
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Old 17th November 2021, 04:23 AM   #2
Nelson Pass is offline Nelson Pass  United States
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Adcom GFA-5800 Cap replacement
At this late date I have forgotten the dimensions of those cans.

I think you want to go to digikey or mouser and see what they have in those dimensions and pick something whose voltage is equal or greater than the original.

It'll work don't worry - it's not actually rocket science.

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Old 17th November 2021, 03:33 PM   #3
exojam is offline exojam  United States
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Nelson,

Thank you very much for your reply.

I was just checking to see if any knew the footprint size so I could go ahead and order them without getting into the amp first (being a wee bit lazy there).

May I ask your thoughts about replacing those transistors like the one I mentioned above? Even if you think they should stay in I think I will clean up the thermal compound and put some new one them. When you do your company’s amp, do you just use a thermal compound or those little thermal pads that see out there (or possibly both).

One last question if I may. What thermal compound is used on the Pass Lab amplifiers?

Thanks in advance, James
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Old 17th November 2021, 03:58 PM   #4
Zen Mod is offline Zen Mod  Serbia
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Adcom GFA-5800 Cap replacement
no need to replace actives if operation parameters are OK

meaning output DC Offset (100mV bracket, +/-) and standing current

re-check screw torque on outputs

if in doubt, post pics
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Old 17th November 2021, 11:39 PM   #5
exojam is offline exojam  United States
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Zen,

Thank you for the reply and information.

I checked the service manual and there is no torque spec listed. Is there basically an industry standard for these type of amps when it comes to that spec, or is it just tightened but not just do not go crazy with it?

Thanks, James
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Old 17th November 2021, 11:52 PM   #6
Zen Mod is offline Zen Mod  Serbia
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Adcom GFA-5800 Cap replacement
if you have torque thingie, 0.9Nm for M3 screws (or US analog)

if you don't have it, use common sense ......... what is important - to check that there are no loose screws
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Old 18th November 2021, 05:50 AM   #7
Nelson Pass is offline Nelson Pass  United States
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Adcom GFA-5800 Cap replacement
It is rare to see screws not sufficiently tightened, much more common the reverse.

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Old 18th November 2021, 05:51 AM   #8
WBS is offline WBS  United States
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Hey! You're up late!

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