6aq5 powered reel to reel tape recorder conversion

[Johnrcurry]

I picked up a tube reel to reel tape recorder at a rummage sale for $5. It uses a 5Y3GT rectifier tube, 12ax7 pre-amp tubes and 6aq5 power tubes in a push-pull configuration. Luckily, it had a schematic glued to the bottom of the chassis. According to the schematic, the power transformer secondaries produce 280 VAC, the voltage to the output transformer is 275 VDC, the voltage to pin 5 of the two 6aq5's is 270 VDC.

I have read that the 6aq5 is essentially a 7 pin, lower voltage 6V6 variant. Based on that, I was thinking of using the guts of this tape recorder to make a 6aq5 version of the Deluxe 5e3. Does this sound like a practical project? If so, would it require a huge amount of changes to the component values from the original 6V6 5e3 circuit?

Thanks

[baddog]

Hi John

If you could post the schematic that would help. I have no experiance with the 6ag5 power tube but what the hell give it a shot. Whats the worst that could happen ? your out $5 . Are you planning on taking the parts out of the reel to reel and puting them in somthing else ore just gutting the reel to reel and modding it? Either way it should be a fun build. you should be fine with the 5e3circuit but anyone else is welcome to chime in.

Baddog

[unparalleled]

Originally Posted by Johnrcurry

I picked up a tube reel to reel tape recorder at a rummage sale for $5. It uses a 5Y3GT rectifier tube, 12ax7 pre-amp tubes and 6aq5 power tubes in a push-pull configuration. Luckily, it had a schematic glued to the bottom of the chassis. According to the schematic, the power transformer secondaries produce 280 VAC, the voltage to the output transformer is 275 VDC, the voltage to pin 5 of the two 6aq5's is 270 VDC.

I have read that the 6aq5 is essentially a 7 pin, lower voltage 6V6 variant. Based on that, I was thinking of using the guts of this tape recorder to make a 6aq5 version of the Deluxe 5e3. Does this sound like a practical project? If so, would it require a huge amount of changes to the component values from the original 6V6 5e3 circuit?

Thanks

6AQ5 is equivalent to 6V6.
For information about tubes try googling "radiomuseum6aq5" (or any other tube number)
Good score! you should be able to make an amp which sounds quite Vox like using the same basic circuit with a tone stack added.
There will likely be another transformer for the tape bias oscillator some where which could also be used for a single ended amp.
I can make more suggestions if I see the circuit.

[Sonny ReVerb]

I built an amp from a reel-to-reel tape player, as well. It also had 6AQ5's. It was an experiment, so I used a cakepan for the chassis. It turned out pretty nice. I used most of the tubes, sockets, and trannies from the tape player. It's close to the Selmer Pro T12:

http://www.schematicheaven.com/barga...o_t12-t_8w.pdf

The Epi EA-50 might give you some guidance, too:

http://www.schematicheaven.com/gibso...-pacemaker.pdf

[Johnrcurry]

Baddog,

My plan is use the parts (transformers, tubes, sockets) to build something else. I'll post the schematic later today, but there is a ton of extra stuff in this machine, and the chassis itself is such an odd shape and arrangement that I think it would be cleaner to just start fresh.

[Johnrcurry]

unparalleled,

There is a bunch of stuff in this machine, including a large choke and at least one extra transformer. There is also a third 6AQ5 tube that seems to be related to the "record" function. I'll post the schematic later.

[Johnrcurry]

Sonny ReVerb,

I looked at the Epiphone Pacemaker, but wasn't sure how the different rectifier and preamp tubes would translate. Your conversion looks like a nice clean, well done job. What circuit did you use?

[Sonny ReVerb]

Thanks, John. I merged the two I posted the links to above. I used the power supply from the Pacemaker, since the tape player had a 6X5 rectifier which is close to the 6X4. I took the pre-amp and power amp from the Selmer which used the 12AX7's and 6AQ5's. Be sure to watch your voltage on the 6AQ5's; they can only handle ~300V as opposed to their 6V6 cousins.

[Johnrcurry]

Here is the schematic for my project tape recorder. . . .

[Johnrcurry]

First, I'm attaching a *.pdf version of the original tape recorder schematic. . .

Here are my questions. . .

The tape recorder takes its B+ voltage from pin 2 of the 5y3 recitifer tube. All the 5e3 layouts I see take it from pin 8. Does it matter? Does it depend on the power transformer? In my case, should I use pin 2 as the tape recorder did, or should I use pin 8 as the 5e3 designs do?

Next. . . Looking at various 5e3 layouts, some put the 68K grid stopper resistors on the board. Others put them at the tube sockets. Is one way better than the other? I've read of something called "Tweed disease," which is described as noise in the circuit, and which is "cured" by moving the grid stoppers from the board to the tube sockets. Is that why some layouts put them at the sockets?

Next. . . Should I use shielded wire, grounded at the input jack end, from the jack to the grid stopper resistors?

Thanks for any help you can provide.

John

[baddog]

I put the 68k grid stop resistor it the unput jack and ceep the leads as short as possible then connect the shielded wire to the resistor and ground it at the input jack where the 1 meg bleed resistor conects to ground . The other side of the shielded wire that connects to the tube isnt grounded at that end. I shrink wrap everthing to keep it neat.

Baddog

[Johnrcurry]

So there's a third option as to where to put the grid stopper. What do you see as the advantages of having it at the jack end?

John

[baddog]

Hi Jon

That is the way fender fender does it. if you get a chance take a look at an old fender amp for insperation. I found that the input is very sensitive and by keeping the resistor and the space it takes up away from other signal paths you will get less cross interference. If the input is close enough to your preamp tube you can try going wright from the input jack to the tube with the resistor itself . I have done that defore and it worked fine. Its your call though. Plus with the input resistor or resistors not being mounted on the board you have extra spaces to mount somthing else.

Baddog

[Johnrcurry]

That makes sense.

Also, I've posted a parts layout (redrawn from the Triode Electronics layout to use 6AQ5 power tubes), and some other questions in the "5e3" forum. I'd appreciate it if you all could take a look and share your thoughts.

http://music-electronics-forum.com/s...9395#post99395

Thanks

John