DR #30 - Adcom GFA-5200 Repair

- Failure: No output
- Quick troubleshooting
- Transistor replacement
- Complete re-cap
- Bias & DC offset adjustments

[@donalddeorio2237]

I bought a GFA535 on Ebay and it was DOA. Contacted the seller and asked him didn't you test it before you listed it. He said he didn't have a pre-amp, told him all you needed was a stereo mini rca to an rca cable and use your phone as a source. He gave me a full refund. The unit looked like a beast, dual mono design with single AC plug. Sent it to a local shop i know and for $160 he repaired it, that was 2 years ago and working great.

[@notfamous3802]

I learn something new every time I watch one of these. Great stuff.

[@SSD99]

Replacing those single-turn quiescent current- and DC offset pots with multi-turn ones would let you dial in the precise numbers called for.

[@akirchner3]

Nicely done sir! Not to spend your money, but if you do much more work like this, consider buying a HAKKO FR301 desoldering gun. Yes it's crazy expensive but it beats the hell out of copper braid for removing solder, particularly from old PC boards.

[@danhorton6182]

Agreed, it’s a game changer. I used an FR301 for about two years and it is now my backup. I grabbed an FR-410 with gun handle and boy oh boy it makes the FR301 seem like a cheap toy.

[@allenwelsch2839]

Hats off to cleaning the pads after removing the components, that's a step many overlook.

[@jameswarren1831]

I sure do love multi-turn pots

[@claudehill2]

Excellent! Well Done.

[@CvetkovIlian]

Great videos and work! Thank you for that but I would like to make a note - this is an audio equipment. Please consider recapping with appropriate capacitors. Termal/temperature rating should not be the most important thing.

[@jeffm2787]

Nice work, I would have used a vacuum desoldering gun to remove all the transistors still mounted to the HS. Hakko or such, not one of those pad destroying hand solder suckers. Braid is fine, just risky for pads and expensive. Overall good job.

[@Phantomas2011]

Love your soldering skills, and watching the whole process!!! Are you using rubbing alcohol to clean the board?

[@dualityrepair4770]

Yep usually just plain old ipa

[@Phantomas2011]

@@dualityrepair4770 Hi ca

[@andymouse]

Another great informative video !...cheers.

[@jameskrivitsky9715]

For the sake of verification, did you test the mosfets to see if there was an issue that made them short out ? Thanks J K

[@emmanuelvallee5386]

Good job as usual. With the exception of the 2 power mosfets, did you have other transistors shorted ?

[@saw1565]

Great job!

[@SifsSwag]

Great work Sir. You need a Hakko 808 solder removing gun. It will change your life! What do you remove flux with? 👍

[@cbfischer]

Great Video... I have the same amplifier, unfortunately the right channel has shorted output transistors. Can you share the replacement part numbers for the pair of output transistors? Thank You

[@rickjames6948]

Where do you repair guys get the schematics from?

[@aurthorthing7403]

That is an odd duck. But I do like it.

[@kdomster9141]

What is the reason some of the rail caps are installed elevated over the board instead of touching the board? Is it for better heat isolation ?

[@fkhan6255]

Hi, what kind of video equipment (camera) did you use to create this wonderful video? Thanks for sharing your work.

[@dualityrepair4770]

Just an Iphone 11.

[@michaelbullock9079]

sounds more like the circuit for the GFA 535 which is dual mono power supply!

[@thomasleerriem6872]

Why doing a third measurement for shorts if 2 sets of pins are already shorted? If B is shorted to A, and C to A, then by deduction C is shorted to B ;)

[@BMC530i]

Nice work! I have the same amplifier GFA 5200. It runs very hot, but does work. Also have the GFA 5200 that has developed a high pitch crackling noise through the speakers when the music stops or it’s paused. Any idea what could be causing the noise?

[@ewingfox6459]

Runs hot because 90% of its life is spent in Class A mode - tons of heat but a great workhorse :D

[@kdomster9141]

I own Adcom 5300 , bigger brother of 5200.... I can recap it but how much would you charge for testing it afterwards and adjusting DC and Bias as you did here?

[@ManojKumar-jk9zb]

Hi, where did you get those caps and fuse to buy? Any site online? Thanks

[@jimwong2823]

Adcom 2535l ? What kind Caps ?

[@sonicfuker]

Good vid. Don't you think that's a lot of work and materials to put into a 50W per channel amp? A 3"x3" chipamp board will smoke that thing in power, distortion and slewrate specs for about how much you spent on parts. Not to mention it will have protection circuits. That Adcom probably thermaled whatever drivers were hooked to it.

[@josephlalock8378]

i'll put up my 5200 against your chip amp any day! mine does 72 watts @1k and 100hz @8ohm/ch before clipping.i havent tested it at 4ohm as i don't want to smoke my cheap dummy loads but it should push well over 110wpc rms. my amp also runs hot and has never thermaled. it now powers a pair of mtms i designed that dips down to 2.9ohm and never hiccups. i doubt very seriously that any chipamp will run these speakers without constantly going into protect or distorting or even just going up in smoke. you should read up a little on 5200s before talking out your ass🤣

[@ewingfox6459]

YES, you can definitely smoke the power output with a more modern amp, but these have very neutral sound. Not to knock modern tech but Pass knew a thing or two about amp design, and his work on the GFA series was quite apparent. Low switching noise and ran nearly all the time in 'Class A' when I tested and used these back in the day

[@sonicfuker]

@@ewingfox6459 Hey man, Pass is a badass, no doubts about it. But wouldn't the amp with higher slew rate, lower distortion and higher dynamic range be considered more "neutral" or accurate?

[@ixfxi]

modern amps are only good until they fail. simply put, they usually dont last the test of time. i have plenty of old and new gear and can attest to the durability of the older stuff. nothing wrong with new, everyone is free to spend their hard earned money however they wish

[@sonicfuker]

@@ixfxi I don't know how you're going to say modern amps are less reliable than old ones. Take a Crown XLi, it's class A/B with every protection circuit that exists, better cooling with superior silicon as far as longevity and reliability. Are there less reliable new amps? Of course, but you're paying pennies per Watt for many times recycled components from China which just didn't exist in the old days.

[@marcdich9066]

I’m curious where you are located I have a pair of GFA 565 dual monobloc amps very large one has a dead rotten fish smell which I’ve been told has bad cabs the other one I’m sure he’s got bad cats also but the sound comes on only when you briefly plugged in the RCA cord but as soon as the ground sleeve of the RCA cord touches the ground on the RCA input sound goes away so anyway where are you located hopefully you’re close if not oh well I may drop these off and have you repair them

[@dualityrepair4770]

Hi Marc, I'm in Minnesota (Twin Cities area).

[@djob3507]

Exelent

[@gnatiu]

Hi there, I have a GFA 5500 for 19 years now. There is a very bad scratch like noise or like a newspaper crumpled up when I turn it on. The thing is: Even when there is no source connected, only the speakers, this noise comes up. Actually I am listening to music with this noise parallel to it. It is very annoying, because I don't turn it up usually. Do you have an Idea what is wrong? Thank you.

[@dualityrepair4770]

To be clear, is this noise only present on power up, or is it always present?

[@gianlucamazzoni1672]

Hi, when will do some tutorial on hi fi troubleshooting?

[@justinhiggins2210]

Nelson Pass designed this didn't he.

[@jimwong2823]

how difficult to replace Adcom input board?also do you know where I can buy the input board?

[@dualityrepair4770]

Not sure on both questions. Sorry.

[@jimwong2823]

@@dualityrepair4770 I could send Adcom amp to U ? If U have the time.

[@dualityrepair4770]

What kind of problems is it having?

[@jimwong2823]

@@dualityrepair4770 bad input board

[@dualityrepair4770]

Send me an email: [e-mail]

[@RanTausi]

Great job !