Hitachi SR-302 light bulb identification

[Nickthedentist]

As a further test, run it at moderate volume into headphones with no speakers connected and see what happens.

N.

[michamoo]

I have an Hitachi SR303L and converted the dial lighting on that to LED. I did use LED strip as someone else has suggested. I completed the job in vivid green and to my eyes it looks great!Cant remember actual details now but i think i did just find a suitable place on the sets power supply section to connect to. Also they dont go dimmer on loud Bass notes like the old lamps did.

[Nickthedentist]

Originally Posted by ms660

Anyone figured out the loudspeaker switch position connections for A+B yet on the schematic?

No, but I have a remarkably similar Trio unit from the same era. Selecting A+B puts the main and remote speakers in series so that the impedance presented to the amp's output stage isn't too low.

[dseymo1]

Originally Posted by jamezx88

You are absolutely right re: speaker wiring causing the overheating. Disconnected one part and it stayed cool for a few hours. Will re-connect using the instructions above.

Re: light bulb. Would these do?

https://www.ebay.com.au/itm/6v-Festo...0AAOSwt5hYicnM

Or these?

https://www.ebay.com.au/itm/6v-Festo....c100005.m1851

Would also be happy to change to LED strip if not too complicated? I think I have one lying around somewhere

No, they would be too bright, might get hot enough to cause damage, and would probably overload the power supply.
If you're not looking for originality, LEDs are the way to go.

[ms660]

Originally Posted by Nickthedentist

No, but I have a remarkably similar Trio unit from the same era. Selecting A+B puts the main and remote speakers in series so that the impedance presented to the amp's output stage isn't too low.

The schematic's on elektrotanya if anyone wants to try and figure it out, I can only figure out A or B, not A+B, unless I'm missing something there appears to be a chunk of circuit not shown on that schematic.

EDIT: Might have sussed it now.

Lawrence.

[ms660]

Originally Posted by ms660

EDIT: Might have sussed it now.

Lawrence.

Doing the R channel:

S6b is the reverse side of S6a wafer but viewed "through" S6A, the bottom two contacts of S6B are connected to the bottom two contacts of S6A so both of the LH ones are connected to speaker terminal A+ and both of the RH ones are connected to the R channel.

S6A (and thus S6B) are shown in the off position, first position clockwise is position A, S6A wiper connects speaker terminal A+ to the R channel, S6B doesn't connect anything to anything.

Next position clockwise is position B, S6A wiper breaks contact with speaker terminal A+ and connects speaker terminal B+ to the R channel, S6B wiper connects to the R channel contact only.

Next position clockwise is position A+B, S6A wiper still connects to speaker terminal B+, S6B wiper connects speaker terminal A+ to the R channel, net result is A+B connected in parallel to R channel.

Next position clockwise is headphones only which is self explanatory.

.....I think.

Lawrence.

[jamezx88]

Thanks again for the advice.

I think I might lack the technical expertise to locate an appropriate spot to power an LED strip so I might stick to using original-style bulbs.

Would these work?

http://www.vintage-electronics.net/f...-6v-250ma.aspx

Thanks,

James

[dseymo1]

Those should be OK.
They'll be over-run by 5% which might shorten their life a bit, but you can always fit a resistor in series if you're concerned.

[jamezx88]

Ended up being able to source some locally (the above link was in the US).

Given the specs assume these will be fine (and won't be over-run)

https://au.rs-online.com/web/p/produ...E&gclsrc=aw.ds

[dseymo1]

Yes, they look ideal!