ok, so i have this univox....i think its a 1050 or 1051 and the output transformer seems, not only too small for the amp, but kinda....badly taken care of and beaten up. my question is, is there any specifications to what kind of output transformer that i could possibly replace it with, or just that it needs to be an output transformer
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changing outupt transformers
- Thread starter BassGuy97x
- Start date
Why don't you get your amp all up and running before deciding if the output transformer is too small. Tube output transformers general have specs like input impedance and output impedance taps, bandwidth and power handling specs you should consider based on the type of tubes you are running and the operating point/tone trade offs. If you didn't already know about this, you may need to do some reading up on tube electronics or get a tech to figure it out. Depending on what the actual power output of the amp is, you could upgrade the output transformer with one from Hammond: regular, Hifi.
Yep. There is considerable effort that goes into specifying an output transformer, I suspect the designers of that amp probably did a fairly decent job.
You must have missed the pics? 4 6L6GC's and what looks like from the iron stack to be maybe a 35 watt OT.
Hi.
In this particular case, there may be a good reason to replace it.
^Yep, this:
http://www.talkbass.com/forum/f15/well-what-973827/
OP, determine first whether the rest of the amp works before putting any serious money in it.
Could be a diamond in the rough, but can also be just a charred piece of coal.
Replacing the OT in a generic X*known tube amp is pretty easy since about all You need to know is the required plate load, F3 point, power handling and the B+.
Since this one is no mystery, someone can probably get the specs or reverse engineer theirs.
Good luck.
Regards
Sam
In this particular case, there may be a good reason to replace it.
^Yep, this:
http://www.talkbass.com/forum/f15/well-what-973827/
OP, determine first whether the rest of the amp works before putting any serious money in it.
Could be a diamond in the rough, but can also be just a charred piece of coal.
Replacing the OT in a generic X*known tube amp is pretty easy since about all You need to know is the required plate load, F3 point, power handling and the B+.
Since this one is no mystery, someone can probably get the specs or reverse engineer theirs.
Good luck.
Regards
Sam
Based on those pics that looked like the stock transformer. 35W looks about right.
Unless the aim was extremely limited bandwidth the size of the PT looks to be capable of 80 to 100 watts.
I would check with the guys at Mercury Magnetics. They specialize in transformer upgrades and chances are they have dealt with that amp before and should be able to give you some good advise on the transformer.
http://www.mercurymagnetics.com/pages/mainframe.htm
According to the 1050 schematic I found, the original is a 3.3K primary, with 2/4/8 ohm output taps. It does look kinda small, so you could upgrade it if you wanted to.
Triode Electronics has a couple of 100W OPTs that would work, but they are either 2.2K or 4K primary impedance, and they have 4/8/16 output taps. So if you're cool with the 4/8/16 taps instead of the original 2/4/8 taps, then you could use either of the Triode ones. Since the primary Z for each is slightly different from the original 3.3K, it's kinda up to you which one you want to try and one may work better than the other - either giving slightly more power, or slightly better sound. Either one would probably be an upgrade from the original, though.
http://triodeelectronics.com/40-18072.html
http://triodeelectronics.com/40-18067.html
Chris
Triode Electronics has a couple of 100W OPTs that would work, but they are either 2.2K or 4K primary impedance, and they have 4/8/16 output taps. So if you're cool with the 4/8/16 taps instead of the original 2/4/8 taps, then you could use either of the Triode ones. Since the primary Z for each is slightly different from the original 3.3K, it's kinda up to you which one you want to try and one may work better than the other - either giving slightly more power, or slightly better sound. Either one would probably be an upgrade from the original, though.
http://triodeelectronics.com/40-18072.html
http://triodeelectronics.com/40-18067.html
Chris
What valves are in it? What voltage is it running at? Get the correct plate load and I'd get it wired for only 4 and 8 ohms
Before we go into a search for a new OPT are we certain how the output stage is configured. It it fixed bias or possibly cathode biased. There some were weird and wonderful ways of designing an amp back in the day.
Link Removed. Fixed bias with NFB. 480 vdc B+.
On the unusual note, check out the plate resistors between pairs and grid resistors between pairs.
On the unusual note, check out the plate resistors between pairs and grid resistors between pairs.
All in the name of saving weight and money. The output transformer is as small as possible, and the component count is as low as possible - it cost some dough to float a boat-load of those things over from Japan back in the day, so every bit of savings counted.
If you are going to go to the trouble of rebuilding this thing, you will probably want to change out all those original capacitors. Those gray ones tend to go out with a bang when they decide to give up. Also note the resistors with one end floating up in the air with wires soldered to them - not exactly mil-spec construction. And all that black around the output sockets is from a previous fireworks show when one of those resistors blew up from a shorted screen tube. And those components floating up on top of the chassis, with one end soldered to the chassis? Wow.
So if you want to clean this thing up, you will need to replace some of the questionable parts, as well as re-doing a lot of the questionable build layout. Components should have both ends attached to something - either tag strip terminal or at least a socket terminal. Get rid of all that free-floating stuff that is just waiting to get shaken down to where it touches the wrong thing.
Good luck.
Chris
If you are going to go to the trouble of rebuilding this thing, you will probably want to change out all those original capacitors. Those gray ones tend to go out with a bang when they decide to give up. Also note the resistors with one end floating up in the air with wires soldered to them - not exactly mil-spec construction. And all that black around the output sockets is from a previous fireworks show when one of those resistors blew up from a shorted screen tube. And those components floating up on top of the chassis, with one end soldered to the chassis? Wow.
So if you want to clean this thing up, you will need to replace some of the questionable parts, as well as re-doing a lot of the questionable build layout. Components should have both ends attached to something - either tag strip terminal or at least a socket terminal. Get rid of all that free-floating stuff that is just waiting to get shaken down to where it touches the wrong thing.
Good luck.
Chris
I did note the blackening at the sockets, they may need to be replaced (not as hard as it sounds).
