Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on February 15, 2012, 01:45:55 pm

Title: Mig 50 EQ Pot Replacement
Post by: plexi50 on February 15, 2012, 01:45:55 pm: I got rid of the steel bar that holds all the cheap plastic pots in place and mounted all new CTS pots right on the chassis
The good part was no drilling required. Reverse wired the outer terminal because of the pots mounting

I also got rid of the wooden standoffs that the board mounted to and replaced them with shorter heigth 6/32 screw aluminum standoffs lowering the board a bit for the CTS pots clearance

Better board mounting and reliable EQ pots

(http://i356.photobucket.com/albums/oo5/plexijtm45/M50OldCheapPotsMounting.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/AlumBoardStandoffsChassis.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/M50CTSPots.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/M50CTSPotsWired.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/M50NCTSP1.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/1966BakeliteBrownChickenheadKnobs.jpg)
Title: Re: Mig 50 EQ Pot Replacement
Post by: gldtp99 on February 18, 2012, 08:01:03 am: Yes i did a similar job on a Mig 50 a few yrs ago---i also replaced the filter caps and the damaged screen grid resistors on the board--- notice that i punched the chassis for 1-3/8" cans for the 1st filtering stage:
(http://i46.photobucket.com/albums/f112/gldtp99/Sovtek%20mig%2050/SovtekMig50004.jpg)
(http://i46.photobucket.com/albums/f112/gldtp99/Sovtek%20mig%2050/SovtekMig50003.jpg)
I used red chicken heads---amp sold yrs ago:
(http://i46.photobucket.com/albums/f112/gldtp99/Sovtek%20mig%2050/SovtekMig50002-1.jpg)
Title: Re: Mig 50 EQ Pot Replacement
Post by: Platefire on February 18, 2012, 09:16:57 am: Looks nice and healthy now and ready for another 20 year run. Platefire
Title: Re: Mig 50 EQ Pot Replacement
Post by: plexi50 on February 18, 2012, 12:52:13 pm: That looks good. I did the same thing on the first filter stage with the first Mig 50 i owned years ago. I really love the deep full growl these amps have. Clean as well. I have it for sale but i dont relly expect to sell it in these economic times. It's better off just staying here with me. There getting harder to find and the prices are steadly going up on them as well
Title: Re: Mig 50 EQ Pot Replacement
Post by: aibonb on January 03, 2013, 01:51:09 pm: Quote from: gldtp99 on February 18, 2012, 08:01:03 am
Yes i did a similar job on a Mig 50 a few yrs ago---i also replaced the filter caps and the damaged screen grid resistors on the board--- notice that i punched the chassis for 1-3/8" cans for the 1st filtering stage:

By any chance can someone tell me what are the values / types for the pots? The bass one wasn´t working and when I opened it found out those old plastic ones and the treble was bad as well. So now since I got it open I would like to change them all. Please advice so I know what to buy. Thanks!!
Title: Re: Mig 50 EQ Pot Replacement
Post by: sluckey on January 03, 2013, 02:08:03 pm: 3 x 1M log
1 x 250K linear
1 x 25K linear
1 x 5K linear

Schematic is here...
http://www.el34world.com/charts/Schematics1.php (http://www.el34world.com/charts/Schematics1.php)
Title: Re: Mig 50 EQ Pot Replacement
Post by: SILVERGUN on January 03, 2013, 02:09:06 pm: Nice work there plexi.....if you get a chance, can you give us some voltage readings before it clears the bench?
Thanks
Title: Re: Mig 50 EQ Pot Replacement
Post by: sluckey on January 03, 2013, 02:14:22 pm: Quote from: SILVERGUN on January 03, 2013, 02:09:06 pm
Nice work there plexi.....if you get a chance, can you give us some voltage readings before it clears the bench?
Thanks
You do realize this thread is almost a year old? :wink:
Title: Re: Mig 50 EQ Pot Replacement
Post by: SILVERGUN on January 03, 2013, 02:17:10 pm: You beat me to it.....I didn't realize it then, but I definitely do now....6 minutes too late.
Thanks

Plex,,,if you took V readings,,,I'd still be interested.........even a year later :wink: :grin:
Title: Re: Mig 50 EQ Pot Replacement
Post by: plexi50 on January 03, 2013, 06:09:41 pm: I didnt wordpad any voltage readings for that amp. I have long ago sold it as well. Sorry
Title: Re: Mig 50 EQ Pot Replacement
Post by: SILVERGUN on January 03, 2013, 06:54:01 pm: Thanks for the response....my friend has one that he thinks he wants me to convert to EL34 (from 5881)
Last time I saw it I thought it had a B+ in excess of 570vdc and I just wanted to compare notes

Have a great new year!