Chris-in-LA
Well-Known Member
PS - I ordered Metrospec transformers from Heyboer on July 22nd for another build and I’m still waiting for word that they shipped. Almost 6 weeks and counting.
Jtm 45 fuse keeps blowing
- Thread starter Marcelcar
- Start date
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Chris-in-LA
Well-Known Member
Can’t tell yet but my Ceriatone JTM45 sounds very close in tone and feel to my Marshall 1987x. I still have to finish my current build before I can compare Heyboer and Ceriatone OT’s.
Chris-in-LA
Well-Known Member
This video helped to convince me about Ceriatone quality and tone.
Nothing wrong with this:
https://www.tubeampdoctor.com/en/output-transf.-for-marshall-jtm45-2xkt66-with-8-16-ohms?c=105
I've used them no problem
https://www.tubeampdoctor.com/en/output-transf.-for-marshall-jtm45-2xkt66-with-8-16-ohms?c=105
I've used them no problem
Nick from Ceriatone just messaged me and said that they don't have any jtm45 OTs in Stock rn and it would take some time to ship. He also said that some multimeters have trouble measuring continouity when facing a high resistance.
He said I had to check out banzai or TAD for replacements.
Does anyone know the TAD OTs?
He said I had to check out banzai or TAD for replacements.
Does anyone know the TAD OTs?
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Chris-in-LA
Well-Known Member
This does look like a good alternative.
Chris-in-LA
Well-Known Member
What is @neikeel ’s opinion on the possible issue with your multimeter?
jhullin
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Trouble Free
Well-Known Member
wouldn't this work I think this is a stock JTM45 OT. Amplified parts (one of our sponsors) lists them says they are in stock ships all over the world and shipping within a day.
https://www.amplifiedparts.com/products/transformer-marshall-output-jtm45
They also have it listed on ebay here
https://www.ebay.com/itm/Transforme...sh=item1ef57fc5df:g:oJYAAOSwAE9cdXk0#shpCntId
https://www.amplifiedparts.com/products/transformer-marshall-output-jtm45
They also have it listed on ebay here
https://www.ebay.com/itm/Transforme...sh=item1ef57fc5df:g:oJYAAOSwAE9cdXk0#shpCntId
As an eBay Associate we earn from qualifying purchases.
Phil from heyboer said that the resistance doesn't matter. If the multimeter doesn't beep, one side of the OT is open. In my case it's the primary.
I think I'll go with the TAD option. Looks reasonably priced and should be of decent quality. Sending the OT to heyboer for a repair would cost me more in shipping than a completely new OT would..
I think I'll go with the TAD option. Looks reasonably priced and should be of decent quality. Sending the OT to heyboer for a repair would cost me more in shipping than a completely new OT would..
thetragichero
Well-Known Member
ot primary shouldn't be anywhere NEAR a high resistance. that would be an issue of open coil (because at that point you'll be measuring the resistance of the air between the break)
I think I figured out why my OT went bad. The impedance selector was turned all the way around, so that it bridged to the top 3 pins (not the three ones that I soldered my OT to). I just tested the contunituy at the switch between the center slot and all the surrounding pins. Even though it seemed from the outide that the selector was in 16ohm mode, it was actually bridging to the 4ohm output that had nothing soldered to... The OT was running without any load attached because there was no connection to the speaker.
A really stupid way to blow a transformer but I didn't even think of the possibility that you could turn the selector around and make it Bridge to the top connections
A really stupid way to blow a transformer but I didn't even think of the possibility that you could turn the selector around and make it Bridge to the top connections
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That is a shame. But explains why we were all struggling. It is why smart arses remind you earlier in the thread to check that you are hooked up to the appropriate load when output tubes are in!
A way to avoid this happening is to solder links to all the spare connectors to the 8ohm tap that way you will never have no load and assuming you will only ever have a half step mismatch if you slip (I do the same with the Orange/Hiwatt plug bases too.
A way to avoid this happening is to solder links to all the spare connectors to the 8ohm tap that way you will never have no load and assuming you will only ever have a half step mismatch if you slip (I do the same with the Orange/Hiwatt plug bases too.
I ordered a new OT from TAD and hope to get the amp finished by Saturday.
One more question. The new OT has a different color code. What exactly does a1 and a2 mean? The b+ wire should go to the filter cap and the 0 Ohm wire to the center of the impedance selector. But where do a1 and a2 go? And why does this OT have a 100v tap?
One more question. The new OT has a different color code. What exactly does a1 and a2 mean? The b+ wire should go to the filter cap and the 0 Ohm wire to the center of the impedance selector. But where do a1 and a2 go? And why does this OT have a 100v tap?
The A1 is one plate(or anode) pin 3 of V4 and the other A2 is the other plate (anode) on V5. I would get a nice new Belton socket to match the other socket and the rectifier base.
The 100v tap is a feature when the JTM45 was an all purpose amp and had a 100v tap for driving long cables to PA gear. You will cut it, fold the end back and heat shrink it nicely like the other wires you did not use on the PT
.
It is always worth leaving those wires too long at first because if you get them the wrong way round you will get positive feedback as soon as you switch on which howls like a banshee if you are unlucky or just motorboats if you are lucky. If that happens on first fire up switch off, temporarily desolder one end of the NFB resistor and retry if the noise disappears then you swap the anode wires around and resolder the NFB wire and retest. Once you have determined the wires are the correct way round you can twist them evenly like the instructions and route them smoothly to the chassis wall round the back of the sockets to pin 3 of the correct tubes. You should get good sound and be able to bias your shiny new tubes in properly.
The 100v tap is a feature when the JTM45 was an all purpose amp and had a 100v tap for driving long cables to PA gear. You will cut it, fold the end back and heat shrink it nicely like the other wires you did not use on the PT
.It is always worth leaving those wires too long at first because if you get them the wrong way round you will get positive feedback as soon as you switch on which howls like a banshee if you are unlucky or just motorboats if you are lucky. If that happens on first fire up switch off, temporarily desolder one end of the NFB resistor and retry if the noise disappears then you swap the anode wires around and resolder the NFB wire and retest. Once you have determined the wires are the correct way round you can twist them evenly like the instructions and route them smoothly to the chassis wall round the back of the sockets to pin 3 of the correct tubes. You should get good sound and be able to bias your shiny new tubes in properly.
Chris-in-LA
Well-Known Member
t
I’ve used 1w and 2w before.
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Chris-in-LA
Well-Known Member
Those switches are confusing. I usually use a meter to check and double check continuity before I solder any wires.I think I figured out why my OT went bad. The impedance selector was turned all the way around, so that it bridged to the top 3 pins (not the three ones that I soldered my OT to). I just tested the contunituy at the switch between the center slot and all the surrounding pins. Even though it seemed from the outide that the selector was in 16ohm mode, it was actually bridging to the 4ohm output that had nothing soldered to... The OT was running without any load attached because there was no connection to the speaker.
A really stupid way to blow a transformer but I didn't even think of the possibility that you could turn the selector around and make it Bridge to the top connections
