Tsl60 Power Transformer Replacement

[cbhuss75]

i am attempting to install a new heyboer PT and am having trouble identifying the primary and secondaries on the board. The new PT has a center tap on the b+. Can this be sent to ground?

The Marshall schematic does not call out what voltage each PT output is, only where they connect to the board and the schematic from the new PT is generic and only gives voltage for each lead.

 

[RCP]

The new PT has a center tap on the b+. Can this be sent to ground?

The Marshall schematic does not call out what voltage each PT output is, only where they connect to the board and the schematic from the new PT is generic and only gives voltage for each lead.

The high voltage center tap goes to ground,
Which model Heryboer PT is it?
The schematic for the PT should tell you everything you need to know.
The PT schematic will show either something like 350V CT 350V Which is the high voltage or 700v(these are not exact voltages) and 6.3v CT 6.3v which are the tube filament heaters.
Sometimes there's no CT/center tap on the 6.3v so you can make an artificial CT using two 1/2 watt 100 ohm resistors to ground.

Knowing the PT model # or posting a pic of the drawing that comes with it would be a huge help

 

[cbhuss75]

I'm not sure on the model, the rep at mojotone said it would be a direct replacement but is is listed on their site as a jcm900 50 watt PT. The issue isn't with the new PT schematic, they list all the wires voltages however the Marshall schematic does not say if w20 is hv 6.3v etc so I don't know where to run the new wires. Looking at the schematic from Marshall, it's hard to trace the circuit to the power tubes.

 

[cbhuss75]

Here is the Marshall schematic. Can you identify the hv, 6.3, etc leads? Thanks for taking a look. http://www.drtube.com/schematics/marshall/TL60-60-02 (2003) iss7.pdf
http://www.drtube.com/schematics/marshall/TL60-60-02 (2003) iss7.pdf

 

[cbhuss75]

The stock one isn't dead yet, I'm replacing it because it vibrates even after tightening. If I measure the resistance at the leads between the sets of wires I should be able to id them I think.

 

[cbhuss75]

Here is s link to the schematic for the new PT. No 6.3v just a 20v?
http://www.mojotone.com/transformers/BRITISH-900-50W-PT.pdf

 

[RCP]

The green wires are 3.15v each which equals 6.3v. These are your heater wires that will go to pins 2 and 7 on the power tubes.
For the preamp tubes one wire goes to pins 4 and 5 and the other green wire goes to pin 9. Green and yellow is the heater center tap which goes to ground.

 

[RCP]

If you look the schematic you'll see the ECC83's (12AX7's) have FILA, FILB, FILC, etc. These are your filament heater connections.
Thats where you'll see the pin 4/5 and pin 9 connections

 

[cbhuss75]

rcp, thanks for the info. That is really helpful.

 

[cbhuss75]

So I've got the new PT and was measuring the taps on the existing PT. All have been identified but I have centertaps on he new PT that the stock one didn't have. I've read that I need to remove the 100 ohm false center if Ike going to ground the new center taps. Questions

How do I identy the false ground resistors on the board?

What is the best place to ground the center taps to the chassis?

 

[RCP]

On older amps the artificial CT usually consists of two 100 ohm resistors going from the pilot lights 6.3v lugs to ground where your 6.3 volt heater wires first go from the PT. Since it's a PCB amp I have no idea where the artificial CT is.
The new transformer 6.3 volt CT simply goes to ground.
Post a schematic of your board and I'll see if I can locate the artificial CT. You may be able to locate the artificial CT by looking for two 100 ohm resistors tied to ground from a 6.3 volt supply.

 

[RCP]

*EDIT* I'm not too sure if R14 and 15 are the from the artificial CT.
I thought it read 6.3V but instead it says 6.3A so I'm a bit leery.
Can you post a decent pic of the R14 R15 area on your board please.


If you can locate R14 and R15 on the board I believe you'll find your artificial CT.
I'm not 100% sure but you may be able to see signs from the wiring of the original PT.

 

[cbhuss75]

Ok I see those resistors. So if cut them I should be able to terminate the centerctap at pin w22 since this goes directly to ground? Thanks for your help. Is there any benefit to using the center tap over the artificial one? Will it lower noise?

 

[RCP]

Please read my edited post above!!!

 

[cbhuss75]

 

[mickeydg5]

Yes, those are the balance resistors, to ground.
The 6.3A is the fuse rating.

 

[cbhuss75]

Thanks, So is just clipping one leg enough to take th out of the circuit or should I remove the resistor all together?

It there any benefit to the center tap over the artificial one?

 

[mickeydg5]

I am guessing Marshall did it for a reason but I will let yo be the judge.

 

[RCP]

The center tap keeps hum down. If a transformer doesn't have a CT then you make an artificial CT.
If you clip or de-solder one end of the resistors and lift them out of the way you should be fine.

If you're leery about clipping/lifting the resistors you can always install the new PT without grounding the CT. Just put a piece of heat shrink over the end of the new CT and It should work the same as it did before.

Any center tap will do. Tapped inside the transformer or artificial, it shouldn't matter which type you use.

 

[RCP]

Anything to report cbhuss75 ?