bogen chb10

[delux1959]

I seem to have to many bogens on my hands. This one has a 7868 output tube. Id like to change it to an el84. Is it really as simple as swapping pins 9 and 7?

[kagliostro]

You must consider some other things like B+, the OT impedance and the fact that EL84 (6Bq5) has a lower output power respect 7868

Franco

[sluckey]

I seem to have to many bogens on my hands. This one has a 7868 output tube. Id like to change it to an el84. Is it really as simple as swapping pins 9 and 7?

No. The sockets are not the same. And you must also consider the electrical characteristics that Franco mentioned.

[delux1959]

I have a noval on hand I could swap. I looked into the pate voltages on the 7868 and messured 430 vdc with no tube in the socket. Im guessing that is to much for an el84. I was looking at a tube data site and it says max voltage for Va is 300 with a 500vdc peak.

[shooter]

with no tube in the socket.

put tube in, does it get close to schematic Sluckey posted, that's your "starting" point, my2c, restore it, sell it and buy parts for a 84 build

[kagliostro]

With that B+ you can use a 6P14P-EV

http://www.tubes.ru/techinfo/HiFiAudio/6p14p.html

but if you can't use an EL84 why change the tube and don't go on with 7868 ?

Oh, I see, 7868 isn't so cheap ...

http://www.thetubestore.com/Tubes/7868-Tube-Types/Electro-Harmonix-7868

http://www.thetubestore.com/Tubes/7868-Tube-Types/7868

Well, go with 6P14P-EV

https://www.ebay.it/itm/2pcs-6P14P-EV-Matched-Pair-Gold-Grid-tube-EL84-6BQ5-Strong/142609594225?hash=item213431b771:g:Yh4AAOSwsFpaIXSk

https://www.ebay.it/itm/NOS-1pcs-6P14P-EV-Gold-Grid-tubes-7189-6B5Q-EL84-5881-6P14P-6-14/142429283470?hash=item212972648e:g:tqAAAOSwgeVZ1SBV

Franco

[delux1959]

just got a 7868 on flee bay for $30 including shipping.

[DummyLoad]

7868 is funky base 7591 - replace socket with octal socket and rewire for 7591 base. electro-harmonix 7591 is 22 bux.


--pete

[sluckey]

What he said!

[delux1959]

i guess i need to keep looking for a schematic. My amp has an ez80 recto. at least to see what the voltages should be. I thought it was the chb10a.

[DummyLoad]

i guess i need to keep looking for a schematic. My amp has an ez80 recto. at least to see what the voltages should be. I thought it was the chb10a.

post a few pics?


--pete

[sluckey]

i guess i need to keep looking for a schematic. My amp has an ez80 recto. at least to see what the voltages should be. I thought it was the chb10a.

The chb 10 has an ez80 rectifier. The chb 10A is a later version of that same amp. It has the ss voltage doubler rectifier. Other than that change, I bet the amp circuit is very near identical. Do you really need a schematic for this simple amp?