Amp parts sources

[Default]

Looked it up and a a 60fx5 is looking for a 3000 ohm load.
Compare that to a 6v6 which is looking for a 5000 ohm load. Any idea what ohm the speaker is?

Looking over at tubesandmore.com, they don't have a 3000 ohm ot, only 2500.
I've bought a couple of these and had good results.

TRANSFORMER, OUTPUT, 8 WATT, SINGLE ENDED ($13.95)

P-T31

Specifications
Power: 8 watts
Primary: 5K ohm single-ended
Secondary: 8 ohm
Mounting centers: 2.375", U-bracket

They also have these for 5 bucks.

TRANSFORMER, AUDIO OUTPUT, SURPLUS, 3 WATT

Specifications
Power: 3 watts
Primary: Audio output 2500 ohm
Secondary: 8 ohm
Frequency Response:100Hz - 40 KHz
Mounting centers: 1.5", U-frame
That's possibly what you have in there, but I'm guessing at this point.

A quick google and this guy says you need a 2.5k tranny. Five bucks, plus whatever else you might need.

 

[Guildmark]

Hey, De!

Would this work? http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=380062126343
Capnjuan knows I've been thinking of replacing the OT and speaker in that little Sears 1420 ce blue helped me rebuild over the summer. It works well but is still pretty quiet. I had been thinking of putting this in, just to see if it improves it. What do you think?
(Chime in, too, CJ.)

 

[Default]

According to the GE tubesheet here, it's also looking for a 2.5k load.
The tranny referenced in the ebay listing would be good for a champ or any other single 6v6, el84 or other octal power tube.
The dual tap on the speaker side is nice, because it gives you a lot of flexibility when choosing speakers.

 

[capnjuan]

Hi Mark; default is one this - that eBay transformer will work for a Champ, Silvertone, Gibson GA5 6V6 Skylark ... or any other amp with only one 6V6 or electrically equivalent output tube but not your output tube. The Hammond 125 series includes a single-ended model with a 2.5K primary and 4 or 8 ohm secondaries. Replacing the output transformer pretty much dooms whatever speaker you have; detaching the old transformer runs the risk of wrecking the speaker which, because it is made of cheese, may not be worth saving anyway. J

 

[Guildmark]

Thanks, Guys! I wanted to replace the fromage speaker, too, John, so no worries there. I'll look for the Hammond OT and a new speaker to try and get this done over the Christmas holiday while the kids are out of school. Then we'll tackle the cosmetics - new tolex and grill cloth. I have no interest in maintaining historical accuracy on this one. This has only been a family project for some hands-on lessons. If we wind up with an okay practice amp, so much the better.

Thanks, again!

 

[danerectal]

I need 8ohm output. Could that be mounted internally. I don't really want to attach it to a new speaker (which is what I will be using as the old one w/ transformer were shot).

 

[capnjuan]

Hi Dane: the Hammond data sheet linked above; see "Schematic & Hook Up Data" section 2/3 the way down, they are offering transformers with primaries (on the left) ranging from 2.5K to 10K and, transformers for example with 2.5K primaries come with 4 ohm (BL and Yellow) and 8 ohm (BL and White) secondaries.

It looks like the model is one of the 125_SE; either A, B, or C where SE stands for single-ended. Chosing which is a function of watts and bias but as little high voltage is in these, the output can't be very much making the A or B the likely choice. The tube data sheet for the output tube usually provides rated output. Yes; can be on chassis, doesn't have to mount on speaker.

 

[Default]

Normally, they are bolted to the outside, but I've seen it done on the inside too.

 

[capnjuan]

Normally, they are bolted to the outside, but I've seen it done on the inside too.

Outside of what? I feel the need for a visual ... aren't Dane's and Mark's amps set up like ChrisB's Dano ... with a metal shelf fastened to the inside of the beaverboard back? ... Eh?

 

[Default]

Sorry, I meant chassis. I was thinking of Stewie and mis-spoke.

 

[capnjuan]

Ok; I don't think that 60XXX output tube is good for more than 3 watts, do you? Mark/Dane: can yousns post some pics of the amps? If they are built like ChrisB's, the electronics are mounted on/around this little metal shelf fastened the back panel. If there's no space on the shelf ... then we'll have to go to Plan B.

 

[Default]

... then we'll have to go to Plan B.

Drink heavily and blame our predecessors? I'm in! Everything I ran into on the web suggested that three watts was all it had to give. Most people who had one seemed to love it.

 

[capnjuan]

... then we'll have to go to Plan B.

Drink heavily and blame our predecessors?

Yes ... but within reason ... ChrisB's Danish Electrode Here showing the original output transformer mounted on the back panel and a new Isolation transformer. Guessing that Dane's and Mark's are similar.

 

[Default]

Ayuh!

Here's what I was thinking of when I posted. Guildmark's project amp.

 

[danerectal]

There are some more pictures of one in the auction I posted earlier.

edit: By the way, my iso. is on the right side by the jacks, and I have a suspended multi-cap. This looks pretty doable.

 

[Default]

Yikes! no fuse!

If you have to replace the output transformer you could either leave it in the same place or drill a hole for the wires and mount it on the tube side. When you replace the cardboard multicap, clip the wires off as close to the multicap as you can. Mount the replacement caps on a couple of terminal strips (pack of 5 at Radio Shack) and use the wires as leads to the terminal strips.

 

[danerectal]

Yikes! no fuse!

I actually have a nice little fuse-ready hole on the left (from the back) side of the control plate. I was contemplating that myself. That raises another question: What value fuse to use?

 

[Default]

I would use a 1/2 amp fuse. That's what CJ from the Maggie list recommended to me for Stewie.

 

[danerectal]

I should mention, the amp in the picture is not mine. If only I should be so lucky. :roll: Mine is in pieces right now. I'll take your advice on ditching the can cap in favor of three individual caps. Much less b.m. This is getting to be a long, albeit focused, thread. :shock:

 

[Default]

I know. It's a travesty, isn't it.