Howdy AKer's. I just bought this Columbia Model C1150-W at an estate sale. The output tubes are 50 C5 . Look just like an EL84. It uses one tube per channel. It has a rather interesting BSR turntable and an tube tuner. The darn thing actually works! I hope there is someone that can help me identify this unit and especially the 50 C5 tubes. As usual, this membership never ceases to amaze me with it's collective knowledge base. I'll thank you now for any help you might offer--THANK YOU!!! :yes:

50C5 is not an EL84. It was designed for low cost applications. Your new hifi is almost certainly a "series string" or "AC/DC" set with NO ISOLATION TRANSFORMER to protect you from the AC mains. Doesn't mean it is junk, but it does mean it's potentially dangerous (50/50 chance of mains AC on the chassis, depending on how you plug it in). You should buy an isolation transformer if you're serious about using it or working on it. BIG EDIT: oops, I see it does have an isolation transformer!!! That's great!

EDIT: 50C5 http://www.pmillett.com/tubedata/HB-3/Receiving_Tubes_Part_2/50C5.PDF

50 V filament
Max plate voltage 150 V
Plate dissipation 7W
2.3 W max output (single-ended, I assume)

Also note it's a 7-pin miniature. An EL84 is a 9-pin tube.

I'll look at the link, but I wanted to thank you first, Thanks Mate :banana: So what kind of reputation does the 50 C5 have? Economy?. Desirable? Have you ever listened to a 50 C5 based amp?

You can find a schematic and parts list in Sams folder 502-7. I doubt I have it, but I'll look.

I have a RCA version.

http://audiokarma.org/forums/showthread.php?t=57236&highlight=50C5

I eventually tried the little amp on my Klipsch Cornwalls, it didn't work out too well at all. Lot's of hum, more like growl.

Wa2ise brings up some good ideas.

If you were getting hum it is most likely a ground loop problem between the chassis of the 50C5 amp which is connected to the powerline via a capacitor and whatever source equipment you are using...had a hum problem when trying to connect a Zenith tube type table radio with phono input to a computer sound card.
I would recommend any "AC/DC" amp which is connected to any external equipment have an isolation transformer.

On the Columbia it looks like the tuner chassis is a conventional power transformer type and that the amp may be a series filament unit which was factory modified with an isolation transformer for connection to the tuner to avoid ground loop issues (and reduce shock hazard).
Probably the cheaper phono only units used the 50C5 amp without the isolation transformer.

I have seen the factory isolation transformer on products such as multiplex adapters and RCA TV's designed for use as video monitors using series string chassis where connections were to be made to external equipment.

"If you were getting hum it is most likely a ground loop problem between the chassis of the 50C5 amp which is connected to the powerline via a capacitor and whatever source equipment you are using...had a hum problem when trying to connect a Zenith tube type table radio with phono input to a computer sound card.
I would recommend any "AC/DC" amp which is connected to any external equipment have an isolation transformer."

I was using a Variac to power it with, (RCA 50C5 amp) but the variac doesn't have a ground pin, so it probably still had a loop. The diode set-up as a half wave rectifier, and limited filtering probably doesn't help matters either.
It seemed more like a 120 Hz growl than 60 Hz, I dunno.

I have a little PS transformer with a 6.3 volt winding, that used a 6X4 rectifier. Use the little OPT's from the 50C5 RCA amp, and swap to 6CU5.
The 6.3 volt version of 50C5....even the 2.5K loading resistance.

Them 50C5's are little glorified dryer elements in glass envelope, don't ever grab a hot one...ouchie!

Jeez....50C5's...there's a blast from my past. Common tube in record players and radios...along with 35W4 rectifiers.