Need a help about tubes!

  • Thread starter Thread starter mixich
  • Start date Start date
M

mixich

New member
HI,
I have a preamp that has ordinary 12AX7 tube (which is an equivalent for the europian name for a tube "ECC 83" ).
Now I want to try an experiment and change the factory tube with one Telefunken tube from my 1955 Blaupunkt radio.Old but good preserved.Anyway none of the tubes I've got is ECC 83.
The tube names are:
ECC 85
ECH 81
EABC 80
EF 89
EL 84
Does somebody knows what are these tubes for and could I use some of them for my experiment with the preamp.
Thanks
 
You can't swap any of those for a 12ax7. They might be a similar size, but they don't have the same pinout and aren't all the same sort of tube.
 
Farview said:
You can't swap any of those for a 12ax7. They might be a similar size, but they don't have the same pinout and aren't all the same sort of tube.
Click to expand...

They all have 9 pinouts as the 12ax7
 
mixich said:
They all have 9 pinouts as the 12ax7
Click to expand...
They have 9 pins, but the pins are not in the same order, meaning that pin1 of a 12ax7 is (for example) the heater and pin 1 of the ECH81 (for example) the cathode.
(I just made that up off the top of my head, I didn't feel like looking it up again to compare what each pin does again.)

I don't believe they are all triode tubes either, so they aren't even the same thing for the same purpose.
 
I took the time to look them up out of curiosity.

The ECC85 is a standard 6V preamp tube. The 12AX7 is a standard 12V preamp tube. The tube heater pinout is different, but the other pins are the same, AFAICT. Specifically, the ECC85 tube has a 6V heater between pins 4 and 5, with a shield on pin 9. With 12A* tubes, pin 9 is a center tap on a 12V heater.

You'd have to make a small power supply change to use a 6V tube in place of a 12V tube. The specific change depends on whether the original 12V heater supply was wired in series or in parallel.

  • Series: If the original circuit has a 12V heater supply on pin 4 with ground on pin 5 or vice versa, you would have to swap in a 6V regulator and add a ground to pin 9.
  • Parallel: If the original circuit has a 6V heater supply on both pins 4 and 5 with a ground on pin 9 already, then the change is simpler. Just replace one of the two 6V heater supply wires (either pin 4 or pin 5) with a ground.
  • Parallel B: If the original circuit has a 6V heater supply on pin 9 with a ground on pins 4 and 5 (why!?!), you would have to remove the connection to all three pins, connect 6V to either pin 4 or 5 and ground the other pin along with pin 9. I doubt you'll encounter this configuration, but you never know. :)

Either way, that tube would require circuit changes, albeit minor ones. The other tubes are hopeless.

ECH81 is a heptode and EABC 80 is a triple diode triode. These tubes are basically designed for specific tasks inside radio tuners.

The EF 89 and EL 84 are single pentode designs and might be comparable to tubes you might find in certain power amplifiers, but would not typically be in anything like a preamp.
 
What you want to do is sell or trade the tubes from your radio for some that YOU CAN USE in your pre amp.
 
dgatwood said:
I took the time to look them up out of curiosity.

The ECC85 is a standard 6V preamp tube. The 12AX7 is a standard 12V preamp tube. The tube heater pinout is different, but the other pins are the same, AFAICT. Specifically, the ECC85 tube has a 6V heater between pins 4 and 5, with a shield on pin 9. With 12A* tubes, pin 9 is a center tap on a 12V heater.

You'd have to make a small power supply change to use a 6V tube in place of a 12V tube. The specific change depends on whether the original 12V heater supply was wired in series or in parallel.

  • Series: If the original circuit has a 12V heater supply on pin 4 with ground on pin 5 or vice versa, you would have to swap in a 6V regulator and add a ground to pin 9.
  • Parallel: If the original circuit has a 6V heater supply on both pins 4 and 5 with a ground on pin 9 already, then the change is simpler. Just replace one of the two 6V heater supply wires (either pin 4 or pin 5) with a ground.
  • Parallel B: If the original circuit has a 6V heater supply on pin 9 with a ground on pins 4 and 5 (why!?!), you would have to remove the connection to all three pins, connect 6V to either pin 4 or 5 and ground the other pin along with pin 9. I doubt you'll encounter this configuration, but you never know. :)

Either way, that tube would require circuit changes, albeit minor ones. The other tubes are hopeless.

ECH81 is a heptode and EABC 80 is a triple diode triode. These tubes are basically designed for specific tasks inside radio tuners.

The EF 89 and EL 84 are single pentode designs and might be comparable to tubes you might find in certain power amplifiers, but would not typically be in anything like a preamp.
Click to expand...

Well thats a hell of an answer!!! THANKS A MILLION!!!Though I was also digging around and I think the 12AX7 tube could be used also with 6V suply but anyway that has nothing to do with my case over here.I've also find out that I could the EL 84 tube in a guitar amp:)And thats about it.
However maybe the best idea now is to put the tubes back in the radio and purchase myself some telefunken 12ax7 tubes from ebay or whatever cause really this sounds like quantum mechanics to me.
But the thing now is that I dont know which tube was on on which slot in the radio:S
 
You must log in or register to reply here.
Back
Top