X-Cans v1 was working now badly distorted again :(

[markb]

Hi Guys,

My X-Cans v1 was working fine for a week or so after the Pink Mods with some Russian Tubes, I just recieved by Valvo PCC189 tubes, same spec but are rated at 7v for the heater rather than 6.3v for the regular 6922's. This should be fine it just means they should last a lot longer.

Placed these new valves in and had a listen for about 30 min. OMG they are awesome...

Anyway put the unit back together and powered up, now both channels are badly distorted

Sigh, I took out the unit again from the case, and replaced the Valvo valves with the previously working Russian ones again and same distortion in both channels.

Any idea what I need to look at, all parts are new, apart from resistors and the DB139's and the other tiny trannies.

I did some checks on the voltages of SK1 connector between the PSU board and the Main Audio board:

Pin 1 = +15v
Pin 2 = +33v
Pin 3 = 0v
Pin 4 = 0v
Pin 5 = 0v
Pin 6 = -15V

So I'm assuming something has gone wrong on the TOP PSU board, Looks like I'm missing the -30V rail from pin 5 I assume?

Does anyone know what these should read?

Any info would be great, thanks guys.

Mark.

[markb]

OK,

So I seem to be missing the -30v rail, I think I have narrowed it down to TR2 on the PSU (BC327), the Emitter (pin3 in this case) has 0v, should have -30v.

Will swap it out... have to pick one up tomorrow for 40c

[PinkFloyd]

Nov 17, 2017 9:23:50 GMT markb said:

OK,

So I seem to be missing the -30v rail, I think I have narrowed it down to TR2 on the PSU (BC327), the Emitter (pin3 in this case) has 0v, should have -30v.

Will swap it out... have to pick one up tomorrow for 40c

Hi Mark,

One of the Panasonic FM caps could have also failed (unlikely but possible) so check the cap that is associated with TR2.

Best regards,

Mike.

[markb]

Hi Everyone/Mike,

Update:

Just replaced the TR2 Tranny the associated Caps were fine, and that did the trick. Sounds unbelievable now with these 1960 Valvo PCC189 (Harleem, Holland) valves. these should last for ages as the heater is rated at 7v. While I had it all apart I also changed R6 to 4.7k, the Blue LED now doesn't burn holes in my eyes

Mark.

Some Pics:

[nando]

Good stuff! Another machine saved.

I thought that transistors only have two options, they work or not but don’t work half. Sounds like you have a half working transistor?

[pingu]

Nov 19, 2017 7:40:48 GMT nando said:

Good stuff! Another machine saved.

I thought that transistors only have two options, they work or not but don’t work half. Sounds like you have a half working transistor?

Yep had this happen to me too. When a tranny is on its way you can get crackles, hiss and what I think the call "motor boating" sounds like a farther little two stroke

Martin

[PinkFloyd]

Nice one Mark, glad you got her up and running again The PCC189 (7 volt) valves are good ones, I've used them a few times and, yes, they should last a bit longer.

All the best,

Mike.