Troubleshoot And Repair This ADCOM GFP-1A Stereo Preamp - Part 2

Follow along as Erik troubleshoots and repairs this ADCOM GFP-1A stereo preamplifier. A discussion on choosing capacitors, how balance potentiometers work, and testing with an oscilloscope are covered.
Part 1 video link • Troubleshoot And Repai...
#adcom #electronicsrepair #preamplifier

[@briang.7206]

Erik's work bench is so clean & organized he's a real professional tech. And Thx for uploading these videos for us.

[@EriksElectronicsWorkbench]

Thanks for the nice compliment :)

[@linjia9539]

The components are much neater and nicer, and even the jumpers on the PCB are straight. Perfect restoration job

[@EriksElectronicsWorkbench]

Thanks! yes I fixed some of the jumper wires too, looked rather sloppy and some were almost shorting together.

[@frankr8271]

I am subscribed to several electronics repair shops on here and you go into far more detail about how and why which is great. You sorta sound like JEB a tech from the OW that did a repair for me as a kid on Keyser St.. Thanks

[@EriksElectronicsWorkbench]

Thanks for watching and I am glad you like the details I cover. No relation to the tech or location you mention.

[@mohimadvani6425]

aah. finally 😊. I am going to watch this after sometime. thanks ❤👍

[@mjg263]

Enjoyed that very much! Thanks for the clear and concise explanation, very good camera work and pacing too. 👏👍

[@EriksElectronicsWorkbench]

Glad to know you enjoyed the video, I appreciate the nice comments, thanks for watching!

[@brianwood5220]

I have really enjoyed this 2 part restoration. So much so, I subscribed and can't wait to check out more of your content. By the way, do you know Paul Carlson? your teaching processes are very much aligned to each other. If I had to guess, I would say you've worked together. Thanks for sharing with us and have a great Christmas break. 🎅🎅

[@EriksElectronicsWorkbench]

Thanks for subscribing and watching! Glad to know you enjoyed the video. Hope you have a nice Christmas season. I have had a lifelong interest in electronics, it's part of my work starting with my first job and studied in college with a degree. I've always enjoyed talking and sharing electronics knowledge and I thought the videos would be a chance to try teaching in a different format and perhaps help others with similar interests especially in troubleshooting and repairs. I have seen some of the fantastic work that Paul Carlson does and drool over the endless cool equipment he has. However I do not know him personally.

[@brianwood5220]

@@EriksElectronicsWorkbench Thanks for replying Erik, Many TH-camrs don't bother.

[@tg_ny]

These are great videos. Are you an authorized Adcom repair center? Question regarding the electrolytic capacitors - is it the amount of time that a component is powered on which ages them, or is it simply time which ages them? I guess the question is whether voltage is the catalyst which ages the caps?

[@EriksElectronicsWorkbench]

My videos and repairs are just a hobby, not an Adcom repair center. I'm glad you enjoyed the videos! Capacitors in general age from both use and time. Some types like very old wax paper and foil age terribly with time as the paper becomes acidic and the capacitor becomes more like a resistor. Electrolytic capacitors can dry out or leak as they age. Electrolytics that remain in use can have a better life span but if that use involves high temperatures, high ripple currents, then it is counter productive and the life may be in the low 1000's of hours. Switching power supplies are very hard on electrolytic types. You may hear the term "reforming" the capacitors in very old equipment by bringing up the operating voltage slowly. This can help but often replacement is the best choice.

[@carlespy7470]

I used to own this preamp a long time ago. It sounded great and I am an Adcom fan. But seeing the inside of this one before you fixed it up leaves me less impressed with the build quality in this instance. The same is not true with my GFA 555 II. Maybe they contracted out the assembly of this preamp?

[@EriksElectronicsWorkbench]

I agree the component placement was sloppy. I have worked on several other Adcom devices and they did not have this build issue. Not sure what happened in this case.

[@sabajochen67]

Hi Erik. Thanks for those great videos. Could you please share a link, where you got the balance poti? Highly appreciated :-)
Best regards from Germany,
Jochen

[@EriksElectronicsWorkbench]

Jochen, thanks for watching. I found the potentiometer on eBay. However I do not think the seller has them now... www.ebay.com/sch/i.html?_ssn=rivervalleylandscapingservice2012&store_name=vermontelectronicsplus&_oac=1&_trksid=p4429486.m3561.l170197 however you might also consider this part ... www.ebay.com/itm/155141896870

[@sabajochen67]

@@EriksElectronicsWorkbench Thanks, Erik! I was able to fix it. Also major issue were the 1000µF and 470µF caps. leaking and short circuited inside :-)

[@user-xe9uw1of1w]

Would you repair my Apt Holman preamp. Right channel went out.
Where are you located?

[@EriksElectronicsWorkbench]

Hi, please contact by email to discuss. If you go to the channel home page and click on the text below the channel title it will bring up an "about this channel" and a link for email.