Tsl60 Power Transformer Replacement

[cbhuss75]

Well I didn't die or blow up my amp so that's good. I wasn't able to get an answer from the PT maker or Marshall support on the b+ tap voltage. It reads 330v when I send one of the two wires to ground but when I connect them to the board posts where the dagnall was, the voltage seems to be split between both wires. I have orders a bias probe from eurotubes so I can safely check my plate voltage. The amp sounds fine but I thought the b+ would have one wire at 330v and the other at 0v so am am concerned. I'm not going o run it much unti I check the plate voltage.

 

[cbhuss75]

I think my bias is set way to cold too. Seems like I read on this forum to set each tube at 37 or so but when using the bias test point on the amp it sees that the mv reading would be BOTH tubes combined. Anyone know for sure?

 

[mickeydg5]

Yes it reads both power tubes at once. You would want 70mV to 80mV.

 

[cbhuss75]

I have not received the Bias probe I ordered yet, but in reading another post from 2011, another forum member was having trouble with his TSL60 blowing fuses. When he measured across w20/w21 (where the B+ plug into the board) he got about 360vac. I'm not blowing fuses an the amp is running, sounding great, so maybe this board just uses both the + and - B+ on the same trace. Looking on the board it appears that they both go to HT1 but one is interrupted by the standby switch and the other is on as soon as the mains are switched on. I'll post the B+ voltage as soon as I get the bias probe.

 

[cbhuss75]

Bias probe from eurotubes arrived yesterday. Worked like a charm. The instructions say that this will read miliamps only so it is only good for biasing however after reading another post on this tool on another forum I can confirm that if you power down the amp and move the leads to the dcv port and select dcv, it will read plate voltage as well as bias for an individual tube. My plate voltage was 432 on one tube and 438 on the other so within the 400-500 spec. My bias does seem to be slightly different between tubes 2-3 ma but i am not certain they are well matched set of el34s. I have another set from eurotubes that were matched at the Portland shop that I am going to try.

 

[cbhuss75]

So it appears that all is well with this tsl60 power transformer transplant. Here is a link to the probe.
https://www.eurotubes.com/store/pc/bias probes.htm

 

[mickeydg5]

I have not received the Bias probe I ordered yet, but in reading another post from 2011, another forum member was having trouble with his TSL60 blowing fuses. When he measured across w20/w21 (where the B+ plug into the board) he got about 360vac. I'm not blowing fuses an the amp is running, sounding great, so maybe this board just uses both the + and - B+ on the same trace. Looking on the board it appears that they both go to HT1 but one is interrupted by the standby switch and the other is on as soon as the mains are switched on. I'll post the B+ voltage as soon as I get the bias probe.

W20 and W21 connect right off of the power transformer secondary HT and is AC power at that point.
The STANDBY switch is after the rectifier network and the HT at that point is DC power with reference to ground.

 

[cbhuss75]

Thanks That makes sense.

 

[Guitar-Rocker]

I am surprised that you aren't having problems with your amp as your posted schematic of the replacement PT doesn't match the existing old PT. Your new PT, according to the posted schematic doesn't have a HT CT, but your posted Marshall schematic shows a CT on the HT secondary, reference W22, W23 the CT, and W24. Your new posted PT schematic shows the PT HT as 335 and 0V with no HT CT.

 

[mickeydg5]

I am surprised that you aren't having problems with your amp as your posted schematic of the replacement PT doesn't match the existing old PT. Your new PT, according to the posted schematic doesn't have a HT CT, but your posted Marshall schematic shows a CT on the HT secondary, reference W22, W23 the CT, and W24. Your new posted PT schematic shows the PT HT as 335 and 0V with no HT CT.

W22, W23 and W24 are for the LT power supply.

 

[Guitar-Rocker]

I stand corrected then, overlooked that.

 

[cbhuss75]

Thanks for taking a look. It makes me a lot more comfortable knowing I've got some more experienced eyes taking a look at my work. This forum is the best!