Suggestions on converting a RCA tube reel-to-reel

[DinoSS100]

Hi,

I found a Rca Victor Orthophonic reel-to-reel at the recycling center. It powered up so I decided to remove the chassis. It has a 6X4 rectifier, 12AX7 preamp, 6AQ5 power tube and an additional 5879 for the recording part or the unit. It seems more complicated than I expected because of the fact that it has the integrated recorder circuit and I don't have a schematic. It looks like a rat's nest inside.

Should I gut it and just use the chassis, PT, OT and tubes to build some bargain bin amp? Does anyone know of an amp that uses this tube compliment that I could use the schematic to build a new one?

Thanks,
Dino

[J Martin]

In this case its probably best to gut it since you don't need the oscillator circuit. You can make a pentode input amp with the 5879 or a dual triode input amp with the 12AX7. Just follow one of the Champ schematics. The 6AQ5 is the same as a 6V6 with a slightly lower power level. Great for making an amp to use at recording sessions. Go to one of the tube info sites and print the pinouts.

[DinoSS100]

Hi J,

Thanks for your response. I searched through Schematic Heaven and found that the Silvertone 1471 and 1481 both used the same tubes I have from the basket case, with the exception of the 6V6. So I guess you're suggesting I just need to convert the schematic to use the pinouts of the 6AQ5. Is this what you suggested?

The only other question I have is on the OT. The reel-to-reel had a 4" speaker and 2 tweeters, I need to figure out the correct impedance to use for the speaker. Can I just use my ohm meter to measure the resistance of the speakers to figure out the impedance of the OT should be?

Thanks Again,
Dino

[J Martin]

Yes, that is the right idea.

Measure the speaker with your meter. The DC resistance will be lower than what the AC resistance (impedance) is, so the actual impedance should be the next standard number up, ie. 4, 8, 16 etc.

[DinoSS100]

Hi J,

Thanks for the help!

Dino

[Jaybird]

You could also try a Kalamazoo model one circuit. Its a great little amp that uses the 6BQ5/EL84, 6x4, and 12AX7 tubes. It is a very simple circuit.

[DinoSS100]

Hi Jaybird,

I've been struggling with what to do with this chassis because conversion to the 6V6 seemed too complicated for my abilities. Your suggestion sounds great and much simplier for me. I'm going to go with the Kazoo, thanks!

I also picked up two Webster reel-to-reels and took one apart the other day. It does not have a separate chassis to use but it has the tubes that go into a lot of the older Silvertone amps. It has two 12AX7's, two 6V6's, and a 6X5 rectifier tube. I've been thinking of getting a chassis and for the next build doing a Silvertone 1392 without the tremolo section. Any thoughts on this project?

I'm assuming the PT is correct for a 1392 since the reel-to-reel had the exact same tube compliment.

Thanks,
Dino

[Jaybird]

Sounds cool! The Kalamazoo circuit you will find to be very easy to work with . I have built three different varieties of the Kalamazoo. I will try to load a pic of one that I did in a Silvertone 1430 amp that had no PT in it and now is a real mean little honker.

[DinoSS100]

Hi Jaybird,

Nice job!!! Thanks for the pics. I like that style Silvertone. I was thinking of building a cabinet in the style of a Silvertone 1333 (an economy version with paint to simulate the aligator/tweed covering).

Thanks for the help,
Dino

[Jaybird]

1333 is cool looking. You can do nice things reproducing cabinets with paint finish in place of the tolex. I did this rebuild with a 1432 Silvertone. I used solid poplar and the acoustics are great. Good luck with your project and keep us posted.

1432 Silvertone rebuilt cabinet.