Search found 5690 matches

by simon
Sat May 18, 2024 10:54 am
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

I bought a few 6AX4s from the US some years ago at a dollar a piece. I've used them successfully with a low voltage GM70 amp. Handily they're octals, but the 6.3V heaters are a pain. I could get some 6V transformers (they'd need to be good for the HT) but the cost will be approaching a 5V rectifier ...
by simon
Sat May 18, 2024 10:47 am
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

Thanks Steve, I've sent you a WhatsApp
by simon
Sat May 18, 2024 9:47 am
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

I've never used 5U4(G). They look to be in current production so there are cheaper options though NOS aren't too far behind GZ37s. Brimar has one at £55 which it describes as "modestly priced".
by simon
Fri May 17, 2024 8:01 pm
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

Great, I'll have 2 please...
by simon
Fri May 17, 2024 7:32 pm
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

£35 for a Hammond 6.3V 3A transformer. Either I'm getting tighter as I get older or this game's getting too expensive for my liking. Toroidy might be cheaper, but delivery will probably even it up compared to Mouser. Are toroids a bad idea for rectifiers? They're supposed to pass more noise than an ...
by simon
Fri May 17, 2024 6:42 pm
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

Mmm yes, good points.

A separate transformer would be better anyway...
by simon
Fri May 17, 2024 5:11 pm
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

On a separate note I do have some 6AX4 damper doodes but they need 6.3V heaters and the trafo only has one 6.3V winding which I don't want to share with a rectifier. Is there any reason not to use a bridge etc. to convert the 5VAC winding to 6.3VDC?
by simon
Fri May 17, 2024 5:09 pm
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

That's very kind of you Steve, and at my favourite price too! It might be a little while before I can get over but I'll be in touch.
by simon
Fri May 17, 2024 2:35 pm
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

Holy cow, when did GZ37s get so expensive? Something else I wish I'd bought a crate of 20 years ago...

Makes SiC diodes look cheap.
by simon
Fri May 17, 2024 2:26 pm
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

Yes, a DIN relay rail octal socket. :shock: The GZ33 lasted just a couple of minutes today before starting to die. There was 5VAC on the heater pins (actually c5.3VAC - perhaps I should pad that down a little?). Whilst I was checking voltage on the trafo's HT windings (not ct) this time the heaters ...
by simon
Thu May 16, 2024 8:53 pm
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

Have you another rectifier to try? (Anything equiv to GZ33) Sadly I don't have any other suitable 5V rectifiers to try. Edit - yes I have one GZ37 somewhere I think. Have you done the unplug, spray with switch cleaner, re-plug in, check socket pins for loose fit, etc. (?) No, not yet but will do
by simon
Thu May 16, 2024 8:51 pm
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Re: Dying Rectifier?

Can't say I've ever heard of anything like that before. Oh dear, that doesn't bode well... Are you certain the 5V is always present at the rectifier? When the sound dies, are the heaters still lit? A GZ33 draws quite a bit of heater current and a dry joint in the heater wiring is always a possibili...
by simon
Thu May 16, 2024 6:08 pm
Forum: Valves
Topic: Dying Rectifier?
Replies: 26
Views: 568

Dying Rectifier?

I think I might have a dying Mullard GZ33, but I've never seen this behaviour before so I'm not sure. I first noticed the sound was slowing becoming quieter, over a couple of minutes or so. Eventually the music stopped and there was no HT. Measuring both heaters and HT winding confirmed there was 5V...
by simon
Thu May 16, 2024 5:52 pm
Forum: Computer Audio
Topic: Yay! New toy
Replies: 88
Views: 101473

Re: Yay! New toy

Looking good Tony. Do you have any tips for getting the connectors spaced accurately on your pcb to mount the I2SoverUSB board? I've played with an Arduino mega footprint in KiCad but I'm not convinced I've kept the accuracy. I probably don't know KiCad well enough.
by simon
Wed May 15, 2024 3:47 pm
Forum: Speakers
Topic: TG "The Loudspeaker" Build (Sort of)
Replies: 168
Views: 16686

Re: TG "The Loudspeaker" Build (Sort of)

Morgan Jones wrote: Wed May 15, 2024 1:43 pm I only have an ancient photocopy of the Tappan paper, but it really can be summarised by the "position braces to minimise the size of inscribed circles" idea.
:thumbright: