Picked up this cool Zenith 2550 Console for a song at the local auction house. Initial idea was to turn it into a guitar amp, of course. Until I got it home, brought it up slow, and it actually sounds quite nice... So I instead decided to pull it from the console and use it as a stand alone HiFi amp. 12AX7 preamp with tone controls and turn table input. 12AU7 gain stage & inverter into a PP pair of EL84/6BQ5 on each side.
The two chassis will be riveted together, and a wooden surround made. Electrolytics are getting replaced of course, as well as some tidying of wires, plate resistors subbed for metal films, and the filaments redone. 'Cause they're really messy! 3 prong cord, naturally, and goodbye death cap. The turn table wasn't working, so none of that business is staying in the PSU either.
It has a slight hum, I'm thinking the above will probably take care of most of it. As well as a balance adjustment for each PP pair that I didn't even try to adjust yet. Cross that bridge when it comes though. Is there anything else that would additionally be recommended?
Zenith 2550 HiFi Recap and Health Check
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Zenith 2550 HiFi Recap and Health Check
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Play your guitar(s)!
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Stevem
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Re: Zenith 2550 HiFi Recap and Health Check
I would add another filter node so that you have no more than two preamp gain stages on one filter and I would make those two filters seperate axial types so you can ground them away from the main grounds on the first two filter nodes that handle the output plates and screens.
I 1K resistor should give enough seperation and not drop too many volts off that new last filter node!
I 1K resistor should give enough seperation and not drop too many volts off that new last filter node!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Zenith 2550 HiFi Recap and Health Check
If those are those waxy caps you might as well check or just replace. also.if you wanna drop.some cash some larger outputntransformers might be a worth while investment 15 or 20,watt edcores would not be toonCostly and would make a nice upgrade. Then you could use the old paper wounds in a future projects,those are.nice amps and usually carry nice tubes one of these days I wanna N do the same thing
Re: Zenith 2550 HiFi Recap and Health Check
Thanks guys!
Steve, you make a good point, I didn't notice there was so much on that node. Attached is more or less what I'll be doing for the PSU. This way I can save the JJ 50/50 cap can I was going to use in here for something else and leave the old cap can on the chassis unused. I like that!
A little redundant for the 12AX7 supply, so I'll probably use a 12 or 10K for that (R52) to take the place of the 2K7 and the 10K which is up in the preamp section along with its 10uf filter.
Menger66, yes, those Sprague .1 600v caps are big waxy ugly's that're getting replaced also. There are more smaller ones in the preamp, about ten of em. Not sure if I wanna dig that deep, but I may replace those as well. New OT's is a nice thought, but ain't in the cards. This is just a quick little project to get it working happy and healthy. After I finish a guitar amp I'm in the process of building for someone I have a big KT77 HiFi amp to finish for myself. So this one is kinda just for kicks.
All the tubes are Zenith branded and most likely original. Pretty sure the 12A_7's are RCA's. The EL84's are "Made in England" and all have the code rx1 B8D.
Steve, you make a good point, I didn't notice there was so much on that node. Attached is more or less what I'll be doing for the PSU. This way I can save the JJ 50/50 cap can I was going to use in here for something else and leave the old cap can on the chassis unused. I like that!
A little redundant for the 12AX7 supply, so I'll probably use a 12 or 10K for that (R52) to take the place of the 2K7 and the 10K which is up in the preamp section along with its 10uf filter.
Menger66, yes, those Sprague .1 600v caps are big waxy ugly's that're getting replaced also. There are more smaller ones in the preamp, about ten of em. Not sure if I wanna dig that deep, but I may replace those as well. New OT's is a nice thought, but ain't in the cards. This is just a quick little project to get it working happy and healthy. After I finish a guitar amp I'm in the process of building for someone I have a big KT77 HiFi amp to finish for myself. So this one is kinda just for kicks.
All the tubes are Zenith branded and most likely original. Pretty sure the 12A_7's are RCA's. The EL84's are "Made in England" and all have the code rx1 B8D.
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Play your guitar(s)!
Re: Zenith 2550 HiFi Recap and Health Check
that 80uF is above the max capacitance for a 5U4. Check your 5U4 spec sheet...
TT
TT
Re: Zenith 2550 HiFi Recap and Health Check
Mullards that another reason those old stereos sound so good they had excellent tubes. I had a cool project lined up a seeburg home stereo console jukebox that I thought was a 6973 tube unite but was really soild state so I passed on it I'm going to try to buy just the speaker though. the changer was messed up on it and I don'twanna mess with it. I have way to many projects going anyway it really bummed me out it was ss. You can just lift one side of those caps to see if they leak. Have fun. Mark