Webcor Reel to Reel conversion thread

Reel to Reel's is a hard conversion piece.
Usually once you strip the R to R section away from the audio amp, the audio chassis is some odd shape that presents quite an obstical to overcome and make something usable out of. Most of the time you better off parting it out and building something totally new with a new chassis. I guess one reason I made it work is I use to enjoy a challenge, but not so much anymore. I find now it hard to justify taking the time to make an impossible project work just to day I did it.

Here is a example of another Revere R to R that the audio chassis was almost an impossible shape to do anything with. I was determined to make it work so I ended up cutting some pieces off and adding an aluminum front plate and back plate to make it work that was drilled and screwed to the original Revere chassis. I build a wood head cab for it and also built a closed back speaker cab for it also. Since the guy that gave it to me went by the handle of "Bear", I called it the "Little Bear". A SE EL84 amps. Here is some pixs and the schematic. Platefire

 

I can tell by the look on his face he was
a little shocked but things are looking up now. Look close at his photo and you can see it. But now new horizons are ahead!

 

That one has two speakers.

If you want to keep it simple, build it as it sits with only the amp parts. I made a small twin speaker amp with a 12cu5 power tube and the two speakers really opened up the sound stage. Not very loud because of low efficiency speakers and only probably 2 watts but it sounds fuller than it should. I don't have any pics of the back but imagine 2 6in. speakers behind the flag.



It is a package set for a friend of mine who is Puerto Rican, and from New York City, and born in 1961, and plays guitar.

@ArcticWhite Really enjoying this thread but more people will get ideas about our supply chain of used parts and those will dry up sooner.

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neat. I think it would be cool to keep the exterior looking as stock as possible. This will be an interesting project, and a really fun amp when it's done.

very cool. I currently have an early 40's bell and howell projector which looks to be outfitted with a combination of rca's and metal covered 'military tubes'. It sounds great as a guitar amp, and won't need any mods, just maintenance. I don't know a ton about amp work, so I made sure to get something that already had a quarter inch input. I paid $40 for it at an estate sale about 4 years ago.

It has a ~5 inch speaker mounted to the case of the projector. It sounds kind of like a low power lap steel amp from the same era, but with an interesting metallic bite on the midrange, and killer punk rock overdrive when pushed with hot pickups.

I doubt I have the fortitude to 'remove all the crap that isn't a guitar amp' like arcticwhite mentioned in the first post, even though there are about 25 pounds of cast metal projector in there. It looks very cool, and I wouldn't want to change the resonance of the cab by removing a ton of material.

 

ArcticWhite

I briefly went over the schematic. You definitely got the tube configuration for a Fender 5E3. I was trying to figure out the output transformer(OT) looking for a 8 Ohm tap but couldn't see one. You also got a choke which is not common for a 5E3 but were common on the latter AB763 Blackfaces. A ton of
of stuff to be de-soldered or ripped out but there is a 5E3 in the midst of it all. Platefire

 

I look at that schematic and see Matchless Spitfire subbing 6V6GT for 6BQ5. Parallel preamp triodes, long-tailed pair phase inverter, push-pull power amp. But that may be pretty close to the Carmen Ghia you already have.

It's extra work, but with an unknown or poorly documented OT, especially with complex secondaries, I would go through the process of applying a known VAC to each pair of secondaries (7VAC from an unloaded heater circuit is convenient), and mapping the voltages across the primaries, which will give you turns ratios of all the different combinations, from which you can calculate impedance ratios.

 

I'd pull that OT out and measure it to get a winding ratio and go from there. Those webcor rtr OTs are oddly configured, but I'd bet there is a good ratio for an 8ohm output in there somewhere with all the taps you have on the OT secondary.

 

I was noticing the overall voltage output of the rectifier is pretty low around 230VDC. That's a little low
for any modern amp types. You could build a solid state full wave doubler rectifier and see what that gets you up to. I think that's what I got built in the schematic on post #41. Platefire

 

Fender Harvard with the lower voltage 220X1.35ish = 300VAC (solid state rectifier) maybe a little higher because of raised wall voltages.

^^This^^ Unknown Output Transformer ID. http://www.regiscoyne.com/tech/unknownOT/ This works, I've done it.

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Of course you could make a Silvertone 1472 out of it! Got the right tube configuration, about the same voltage, I think it's the easiest thing to get to rewiring existing. The voltage might pick up a little bit once it's decoupled from the tape player part. Might be a good idea to remove the tape player part first and then fire it up, see what you got
Voltage wise and plan from there. I kind of doubt it will change very much but may be worth a try. Platefire

 

Tweed Vibrolux is basically Harvard with a "wiggle". I only mentioned the Harvard because of the voltage of your power transformer.

Dearmond R5 (single 6V6), R15 or R15t all lower voltage with great reviews.
Check out LeonC DeArmond R5T and R15 videos.

It's easier than it sounds.

I use a small 6v wall wart transformer with AC output and follow this guide. You have to check the actual voltage out of your wall wart because of "No-Load"


The Turns Ratio (TR) can be found by applying a small AC voltage to the secondary and measuring the result on the primary. If you put 1v AC on the secondary and measure say, 31.6v on the primary you have a Voltage Ratio (VR) of 31.6 which means that the turns ratio is 31.6:1.

Finding a 1v AC source is difficult unless you have access to a Variac, small transformer or similar device.

You can use a 5v rectifier winding from an existing PT or the 6.3v heater winding. You must then divide the answer by the number of volts you applied to the secondary.

For example the 31.6:1 TR would measure 158v with 5v AC applied to the secondary.

The Impedance Ratio (IR) is the square of the Turns Ratio (TR), in this case:
31.6 (sq) is 998.6

To determine the expected Impedance Load (IL) or speaker impedance you will divide the known Effective Load Resistance (ELR) by the Impedance Ratio (IR)
So: ELR / IR = IL

In this example we want to use a pair of 6V6 tubes that have an ELR of 8,000 ohms with this transformer and want to determine the proper speaker impedance (or IL)
8,000 / 998.6 = 8.0 ohms

So you would use an 8-ohm speaker with this transformer and a pair of 6V6 or EL84 tubes in AB1 or AB2.


Give it a try! It looks like the possible choices for output are going to be...
1-Blue/Black.
2-Brown Yellow.
3-Red_Black/ Grn_Wht.

You already know the input color code.

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