PSU III transformer information.

[bob orbell]

Hi all, many of you may know that I use two power supply's, one for Pre the other for Phono, can someone give me information about this transformer used in Phono, it continually pops the HT regulator I made and fitted, the other works fine. It has just popped again and on the bench I am reading 318 volts AC, and 420 volts DC, unloaded, obviously, too high, this transformer is a bit larger than the other one which is from WAD days, the one with the problem is from WD, it is made by Tiger Toroids Ltd, part no. TT1641, there are two more no's. P.01379 608868 and F.01379 608871, there are no voltage ratings, pri or sec, can anyone help please. Bob

[John Caswell]

A schematic and further transformer information would help.

John

[bob orbell]

John, it is a WD PSU III, I added a home made HT regulator to the output to drive a WD Phono III, I have now removed the regulator so the PSU III is as standard and I have this very high voltage from the red and black leads, voltages as in post one, I spoke to Matthew yesterday and he confirmed the transformer is from the Dave C era and has given me the resistance readings of one of his transformers, I will take readings this morrning. Bob Update, pri reading between brown and violet- 42 ohms, same between grey and blue, secondary between red and black 156 ohms. Bob

[Richard]

Hi Bob, maybe Dave C had some for evaluation. How did you end up with it, a kit or parts from when Peter left? Tiger has contact details here so maybe drop them an email for the spec, https://www.tigertoroids.co.uk/
On a practical level, can you try a dropper to get the rectified DC into the ball park then fit the reg again, that should work fine I think, as it it sounds like the reg is having to do too much work with the extra voltage at the moment doesn't it?

[bob orbell]

Thank you for the reply Richard, and John, been on the bench this morrning, PSU returned to as original, no regulator, loaded DC reading at phono output 320 volts , changed R6 to 33k, voltage loaded 250 volts , voltage at C1 almost 420 volts, a bit to close to the value of C1 and C2 given 20%. I will drop Tiger a email with all the details and no's. Transformer came from one of our regular members, but can't remember who. Bob

[bob orbell]

Update, just spoken to Tiger and this transformer is one of ten that went to Arena, this I believe was Peter C, Tiger never got payed for them , the next batch Tiger made were for Dave Cawley and have a different batch no so, I will get a new one from Matthew. Bob

[Richard]

Hi Bob, that's good, do you need a new TX?
I don't know what reg you're using but if you set it up again as a passive supply can you then find a dropper R to leave just enough over-voltage (280V to lower to 250V or whatever excess the reg needs) for your reg to work in comfortably,
so it would end up, TX > Rect > Dropper > Reg rather than letting the reg try to cope with too much voltage?

[bob orbell]

Yes I could do that but, as in my last post C1 and C2 are seeing almost 420 Volts, that is too much for comfort, I could change R1, but have already ordered a new transformer from Matthew, it's only money after all and I will be more happy with the lower voltage. Bob

[Richard]

Put the dropper at R1 before the caps rather than R6 after?

[John Caswell]

A very common problem, that I strike regularly, is that the transformers, unless specifically requested, are wound for 230V.
This does cause problems on 250V ie 10% up. 13A plug in types often called "Wall warts" are notorious for this.
A range of Thorens T/T use a 16V ac input, but depending on the supply and current drawn I have measured these at 20-21V - disastrous in some cases..
The mains supply in the UK varies drastically, I have a couple of customers local to me who's supply is regularly 253-4 during non peak periods.

John