Let's Repair this buzzing 1959 Ampeg M12
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- čas přidán 25. 07. 2024
- This Ampeg M12 was unbearably noisy. Let’s look at how we test the main circuit suspects. We will also test the more common tubes with my MaxiMatcher 2 and the more obscure ones with my trusty old B&K 700.
We will revisit the definition of ESR and use this knowledge to test the likely longevity of the electrolytic capacitors to help us decide if they stay or hit the bin with an unceremonious “ping”. I am a stickler for retaining as much of the original componentry in a vintage amp as possible and sadly too much of this gem was devalued by previous work.
If you thought biasing a self-biasing amp was not possible then stay tuned to see the methodology.
As always, please DO NOT DO what I show you in these videos. One slip and you will suffer a severe case of death.
Video Index
00:00 Introduction
00:48 Overview of the Ampeg’s condition
03:30 Applying power … slowly through Variac and Stepdown transformer
05:43 Dating the Transformers
07:00 The Multi-Capacitor can
07:30 Testing the Tubes on the MaxiMatcher and the B&K 700
13:08 What is the Equivalent Series Resistance
14:20 To Replace or Not to Replace the old waxy capacitors…that is the question.
16:55 Why no switching earth on the input sockets?
20:30 The decision to replace the input socket
22:10 How to bias a “Self-Biasing” Cathode bias output stage.
33:20 Wrong fuse. Replace fuse holder. - Hudba
Good to see you back. Good morning from Chicago!
G'Day Dennis. Thanks, mate. You are in great part of the world with wonderful music. I did a show in Chicago in my gigging days and soaked up the downtown vibes in my 3 days off. I was talking to the drummer of a little jazz band I saw and he sounded like me trying to do the cliché 20's Capone voice....only it was his real voice!
Hey Chris, another great video and I love your sense of humor!😁🎸
Thank you Markus. I really appreciate your comments!
Good job! Boy I sometimes forget to check the fuse first. I once found a 20 amp!
Chris, I have a '59 Ampeg M12. Some (like mine ) have 12ax7 preamp tubes. I love the tolex on Ampegs from this era.
I really enjoy your channel. Thanks!
I love that tolex pattern, too! Wow! A 20A fuse??? I've seen a 10A, but you've just found a new record in stupidity. Good find.
I did a similar J-12 Jet from 1960. Yes, every coupling and trem osc cap was leaking DC and needed to be replaced as well as all plate resistors which drifted wildly. Really nice sounding amp when I was done. Yet another "Why the hell did I sell it then?" moment... Love your vids, Chris. Greetings from NJ USA.
I feel your pain. Its really hard to decide how much to replace on these classics before we turn them into mere clones. I get around it by asking the owner of his intentions with his amp. If its to gig or record, sadly I need to replace many sus components. If it for home or collecting, I just get it working and leave as original as I can. After all, we have to be responsible custodians of this musical history. Greetings from Sydney, Jersey boy!
Hey Chris....Nice amp, oldie but goodie...The math boggles me a bit still, but I'm trying to get a grip..Great walk thru and repair info..Methodical and great learning video..Top job as usual..Stay safe..Ed..uk..😀
Ed, I am your greatest fan. You always have something positive to say on my videos and all the other great Techs you comment on. Thanks mate.
@@theguitaramptech All you guys are awesome..👍
Hi - Thank for posting this video. I'm in the midst of restoring the very same amp. Almost the same year too. How did it sound with that speaker?? Mine still has the original Jensen C12R and it sounds very brittle. I'm going to check the bias on mine with your method. Cheers!
What a cool project, David. Sometimes the Jensen can sound a little brittle. The best advice I can give you is to call CJ Sutton at Weber speakers, and tell him Chris recommended you. CJ really knows speakers and how to solve your issue.
The Ampeg sounded rich and full after the work was complete.
@@theguitaramptech thank you for the advice. I'll give Weber a call.
👍🙏
Another great video, Chris. That vintage tube tester is a beast. Is it accurate? I can tell that there was technical issues with this video. Sometimes simpler is better. Still loved the video!
Thanks Les. Yes, the B&K is from the days when the world ran on tubes, and not just guitar amps. It covers more tubes than I have ever heard about, let alone used. I calibrate it every year. It stays remarkably stable.
In my effort to make more interesting videos, I just got myself in a tangled mess during editing with syncing 2 cameras and then deleting scenes during periods of frustration. Lesson learned.
😄😎
Thank you FMF
@@theguitaramptech I learn a little bit about amps from all the video I watch - I have 17 amps
@@user-dz1fq2di1g 17!! Thank God. And I thought I had an amp collecting fetish.
@@theguitaramptech I purchased a rare amp, a Budsen with Partridge Transformers 1960-66. Can't find info about this amp? It's a tube amp with point to point wiring and never been touched.
@@user-dz1fq2di1g that’s cool, FMF. Good luck with that project.
Bonjour à vous. Je suis tombé récemment sur votre site et je me permet de vous demander conseille.
Je révise actuellement une tête Ampeg SVT VR et l’ancien propriétaire suite à une réparation c’était fait installé un condensateur supplémentaire. Que je vais essayer de vous situer sur le schéma.
C’est un condensateur(X). 450v 47uF soudé entre le négatif de C27 et le positif de C29 ensuite un bout de câble et soudé du positif de (X) directement sur R60 (47K 5W) et donc ma question vous me conseillerez de retirer (X) ou est ce que ceci à été installé dans un but bien précis que j’ignore hélas ?
Et je trouve que la tête fait beaucoup de bruit même à volume bas.
Merci pour aide. Dan (de France)
It is very dangerous for me to offer advice like this, Dan. If I understand your question correctly, Capacitor X is connected across C29. He may have been testing if C29 was working correctly. To connect the positive of C29 (320V) to R60 (480V) looks wrong. I cannot give you any advice about what to do with such dangerously high voltages. Check the connections again. Then check them again.
Bon chance.
Bonjour
Autant pour moi ce n'est pas C29 mais C28 (Le + de C28 relié à R60) et le + du condensateur (X) au + de C28 et le _ du condensateur (X) au -_ du C27. (Si je pouvais envoyer un schéma ce serait plus simple. . Il y a aussi un câble avec masse flottante qui est soudé entre J6 (pin1) et R55. Bonne continuation. Dan
Bon j'ai fini par trouver il a doublé la capacitance de C28 (450V 47uF) avec ce condensateur (X) (450V 47uF) . Portant C28 et encore bon..
Bon il me faut régler ce problème de bruit . Bonne journée. Dan
@@gibbons192 Bonne journée, Dan. Chris
Please hold your camera steady
What did you think of his expertise despite the camera issue..? Great tech eh..!
Thanks for the observation JD. Yes, I had clearly reached the end of my camera and editing abilities. I was trying to do 2 camera work using my GoPro for my B-roll and it was a nightmare to record and edit. I am embarrassed to say how long it took to edit this video, PLUS I lost footage somehow. I have found my level of videographic incompetence! I will stick to one camera recording from here on in.
@@edwardhannigan6324 I love you Ed! I am not sure how many beers I owe you when I finally get to the UK, but I am pretty sure I will be leaving you with a drinking problem!
@@theguitaramptech No worries....Some people need to see the big picture..Stay well..Ed..👍