Adcom GFA-535... Pics... is THIS Stock?? - Page 2 - diyAudio
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Old 13th May 2009, 08:47 PM   #11
777funk is offline 777funk  United States
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Quote:
Originally posted by adason
wow, I just noticed the fuses on that thing!!!!!
if that thing blows, it takes everything with it
I would replace those fuses with correct ones if I were you
I had read here on this forum that the B+- fuses to the power transistors can limit the current to them resulting in poor sound quality. Especially with corrosion on the terminals. I read a few people saying that it sounded better with them jumpered. So, that part of the amp is definitely non stock. Good eye! I saw the two red caps and that was what I was wondering about mainly. I'll have to give it a good look over.

My thought on the fuses is what are the chances the power transistors are going to go bad. In the case they do the current will pop the main fuse (hopefully). Most audio amps I've seen don't fuse the power supply to the transistors. So I figured that since the point of this thing is to sound it's best, I'll change parts if something does go.
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Old 18th May 2009, 09:29 PM   #12
sonidos is offline sonidos  United States
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Those caps are on my unit as well (sorry, I'll have to check the schematic later). Those are stock as I bought mine brand new and never modified.

If you go to diyaudioprojects.com, I'm doing a rebuild of the Adcom 535 psu listed in the solid state section of the forums and upgrading my resistors to Dale Vishay, plus replacing all the electrolytics.
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Old 19th May 2009, 12:17 AM   #13
sonidos is offline sonidos  United States
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Here's a photo I took before upgrading the resistors, caps, and trimmer.
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File Type: jpg right_before.jpg (91.2 KB, 335 views)
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Old 19th May 2009, 12:52 AM   #14
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Quote:
I had read here on this forum that the B+- fuses to the power transistors can limit the current to them resulting in poor sound quality.
Hmmmm , The fuses might be there to prevent a fire hazard , or to keep the phenolic board from actually burning up. My screwdiver recently slipped and instead of having 8 burned OP devices and exploding screwdrivers , just 1 $.70 - 7A fuse was all I needed. If you are worried about a current "bottleneck" at the fuse , a couple of 2200-3300uf/63-80V caps soldered right at the PCB OPS rails will still offer protection while giving a little more headroom.I have a {C-C-fuse-C} setup and can see a .1mv drop right after the fuse , but at the last cap (6800u - on PCB),nothing at all.

Or at least a slightly over-rated fuse would offer "dead- short"
fire /PCB protection.

OS
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Old 19th May 2009, 01:37 AM   #15
sonidos is offline sonidos  United States
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I can tell you from experience that those fuses are there if the speakers are shorted!

One of my stepkids, that to this very day has not confessed, but they removed the cables from the speaker binding posts and put the + and - of one channel in contact with each other. I found the cable sitting on the floor. I immediately hooked everything up and the left channel was dead.

I opened up the amp and one of the fuses had blown. Got a replacement and I was back in biz. As you can imagine, I raised holy heck and nobody has touched my stereo since that time.
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Old 19th May 2009, 01:17 PM   #16
sonidos is offline sonidos  United States
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Default Adcom 535 schematic

Here's a link to the schematic



diyaudioprojects forum w/schematic
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Old 19th May 2009, 06:01 PM   #17
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Hello,
could you please post the schematic on this forum?
Many thanks

Marcello
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Old 19th May 2009, 06:43 PM   #18
sonidos is offline sonidos  United States
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Hello Marcello,

I'll check with policy on posting schematics for commercial products. The moderator for diyaudioprojects.com was nice enough to permit me to post it on his site and I don't want to violate policy on this board.

If I get the okay, I will post it.
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