Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: simonallaway on October 28, 2014, 10:20:20 am

Title: Unknown power transformer - Bluesboy 700V
Post by: simonallaway on October 28, 2014, 10:20:20 am

A power transformer has fallen in my lap, but I cannot find any online documentation about it.

It has a sticker on it that says "BLUESBOY 700V PT 9960424". Probably due to inexperience I cannot infer anything from that. I'm getting ready to use a multimeter and signal generator to see what I can find, but I thought I'd ask here as well.

Thanks,

Simon

Title: Re: Unknown power transformer - Bluesboy 700V
Post by: sluckey on October 28, 2014, 11:00:58 am

I would use an ohm meter to determine which wires connect to each other. Group all wires that have continuity. These groups will be the individual windings. Then determine which winding is the primary. A variac or a filament transformer is handy for testing but if I'm pretty confident about which winding is the primary I don't have any reservations about connecting it straight to the wall. Watch for bright sparks and smoke and stinky smells! Then just measure all the secondary voltages.

Title: Re: Unknown power transformer - Bluesboy 700V
Post by: HotBluePlates on October 28, 2014, 07:47:51 pm

"996" is the EIA code for Heyboer. I assume "700v" means 350-0-350v for the high voltage secondary.

I'd probably email Heyboer and ask if they have a wiring diagram for this transformer.

Title: Re: Unknown power transformer - Bluesboy 700V
Post by: simonallaway on October 31, 2014, 10:32:04 am

An excellent idea! Heyboer responded almost immediately with a diagram. I attached it to this post for the record.

Thanks!

Title: Re: Unknown power transformer - Bluesboy 700V
Post by: simonallaway on October 31, 2014, 11:05:55 am

Would it be true to say this PT would be suitable for an AB763 build?

Title: Re: Unknown power transformer - Bluesboy 700V
Post by: DummyLoad on November 01, 2014, 01:44:48 am

15-20W amp w/ trem and reverb. build a PR with it. build a pro 5e5 - it fits...mostly. 1/2A over on the 5V filament for recto.


roll your own w/ 7591... 450V B+ Rload 8K-9K cathode bias.


--pete

Title: Re: Unknown power transformer - Bluesboy 700V
Post by: DummyLoad on November 01, 2014, 03:27:33 am

just doodling... if i had the parts, i'd breadboard schema attached... and other pre-amps circuits: a marshall or, TW, or probably something totally out of left field....  :icon_biggrin:


as long as you don't use more than three 12A_7 bottles, filament winding remains within the current rating.


--pete

Title: Re: Unknown power transformer - Bluesboy 700V
Post by: simonallaway on November 03, 2014, 12:07:20 pm

Ah! So one can sum the current draw of certain elements of the circuit and see what gives? I should've thought of that.

I like the idea of a Princeton Reverb so I'll probably go in that direction. I'm definitely looking to build a classic Fender design rather than something very different. I was brought up on Marshalls and Les Pauls so I feel like I need to get to know a 'true' Fender tone. Especially one that'll fit well with a Tele/Strat, which is something I've never had much luck with.

Thanks very much for the doodle. It's an interesting idea, but perhaps for the next project.