Electronics > Repair

roland 808 drum machine u.s power conversion

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squadchannel:
Triad F3-10 for 10V and
Triad F4-36 for 23V.

f3-10:$7.43
F4-36:$9.52

What do others think?

dual output transformers were hard to find.
now that we know we can get two put in, anything would be possible.

cod65:

--- Quote from: DimitriP on January 07, 2025, 08:49:10 am ---
--- Quote ---As I mention above this does not have the original transformer but 2 modern 230vac tformers currently[/
quote]

"RS-Pro"  no less :)

RS PRO 6VA 2 Output Chassis Mounting Transformer, 9V ac, IEC 61558-2-6
https://docs.rs-online.com/cd7c/A700000008857656.pdf


RS PRO 6VA 2 Output Chassis Mounting Transformer, 20V ac, IEC 61558-2-6
https://docs.rs-online.com/9099/A700000008857672.pdf


one has two  secondary 9V windings 3VA each, the other has two secondary windings  20V  3VA each ..

It's right there on the label...

and I forgot what the original question was ....

--- End quote ---


thanks Dmitri. Some other details I would like to add(should have added earlier): I have a remote 'mentor' that I asked about this project. I told him the same information you pointed out - that the existing transformers had ratings of 3VA,6VA. I calculated that the transformer current max  then must be:

9vac:
2(3VA) = 6VA(parallel config) so I = (VA)/V = 666ma

and 20-0-20:

I = 3VA/20 = 150ma each leg

I says 'why dont  I just get some similar 3VA 120vac transformers ?'

he insists a couple things: that the fuses, being 500ma imply that the transformers have to handle at least 150% of that, or they will blow first. Hmm I says- and then i look for weeks realizing that nothing would fit in the 1.7" space I have to work with !  Frustration ensues.

He says: you dont know the current based on the schematic - it seems to say 150ma secondaries , but you dont know if that is peak , etc. not fully clear, and because you don't know the current you need to rate above the fuses by 125-150%

I says OK.  And, of course not many transformers of that rating fit in a space no more than 1.7" high. I figure maybe I use toroidal. Then I figure maybe I will ask more people before I proceed.

He also says he doesn't use voltamp ratings for transformers becasue he considers them to be a kind of gimmick among manufacturers and not a reliable way to go -stick with max current rating - hmmm.... OK. He is way smarter than me so I listen. But then I realize many manufactures only list voltamps. I read up on voltamps and it seems pretty straightforward to me - I even see that these transformers CLEARLY SAY 3VA. But now hes got me vexed , and I want to ask more people , etc. This is partially why I am here.

so, yeah, I was initially under the impression I would just look for appropriate 3VA rated transformers and be done.  But he got me all scared and I want to understand what all the experts are telling me 110%

thank you for your knowledge and time!




--- End quote ---

cod65:
I would also like to mention I chose early on for 9vac secondary , and have on hand , Hammond 187B10. It has ratings of 115vac ,10Vct, 6VA. It would fit well . does it look copacetic ?


https://www.hammfg.com/part/187B10




squadchannel:
no problem i think.

if hammond, 23V choose 187A20 or 187B20.

187A20 is slightly lower current rating. maybe insufficient.

Toroid are overkill and a waste of money.

cod65:
i measured a max height of 1.7" available  inside case, this hammond is similar to existing at 1.37"

looks like 187b20 will fit also ! thank you !

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