TSE pre checkout check.

[mudchute]

Hey all,

I've put my 300b SE together ready for its first check and adjustment (I hope) but I would like to double check my wring first particularly the volume pot.

I'm using the Edcor XPWR131-240 PT.

So far I have:

TI-1 = White - HV centre tap
TI-2 = Yellow - 2.5v
TI-3 = Yellow - 2.5v
TI-4 = Orange - 330v
TI-5 = Red - 330v
TI-6 = White/Brown - 3.15v centre tap
TI-7 = Brown - 3.15v
TI-8 = Brown - 3.15v

The remaining transformer wires, are these used? Unless I've missed something I'm assuming they're for other configurations? These are:

White/Yellow - 2.5v centre tap
White/Orange - 260v
Black/Red - 260v

Re the volume, I'm guessing:

L-1 = Left channel ground
L-2 = Left channel signal

R-1 = Right channel ground
R-2 = Right channel signal

Thanks guys.

Will it all go up in smoke...

 

[mudchute]

Oh, I assume GND-2 is for grounding?

Is there anything I've missed?

 

[mudchute]

I took the plunge, Board is grounded, everything hooked up and first power up done.

With the rectifier tube in and nothing else I'm getting 425v of b+.

I need another meter before I can start on the rest. Is it fair for the b+ to be so high with no other tubes in?

 

[mudchute]

So, here I am so far.

B+ is 345ish volts.

Both 300b's are stable at 69ma.

Both driver tubes are stable at 177 volts.

Sounds great so far, concerned that the drivers tubes, on start up are drawing big volts before settling down, mid 200ish volts, is it a time bomb? I have a cl90 on the iec's live terminal, can I put one elsewhere?

Also, I have 36k resistors in r25 & r14, I was expecting a b+ of nearer 400v?

 

[mudchute]

Happy day today

 

[YashN]

Way to go, mudchute.

 

[mudchute]

Thanks Yashn, hopefully Itll stay in one piece...

Is it safe to couple the heatsinks to the chassis? The current ones are isolated from the components but it seems awfully risky...

 

[mudchute]

First start up today. The 5842 voltages are concerning. The left channel goes to approx 200v then settles to 170v. The right channel goes to just over 300v before dropping to 170v. The right channel also lags behind the left in playing music and r9 is turned down a good amount less than r20?

Should I be worried?

I've swapped the 5842's around and the fault followed the tube...

 

[JP]

Normal. The voltages will be high until the tubes start conducting, and the adjustment was added due to a high variability between tubes.

 

[mudchute]

All working and stable so far.

Re grounding, I've grounded the board direct to the iec and put a grounding stud near the iec and grounded the chassis from that to the iec.

Am I supposed to ground anything else?

I've got no hum or other anomalies occurring.

 

[JP]

The ground side of the output transformers secondaries should be connected to your IEC ground for safety.