So they sent me E88CCs ?

[gtrplayr1976]

Company I bought my 18 watt kit from sent me E88CCs for preamp tubes. Aren't these made for HIFI ? If any of you wise men would take a look at my post in Debugging maybe you could help me with some issues, give feedback on wiring , what I can do to make it better ?

Thanks a heap !

[J M Fahey]

No big deal, should work similar to 12AX7 but remember filament wiring is different so they are not directly interchangeable.
Check both datasheets.

[gtrplayr1976]

No big deal, should work similar to 12AX7 but remember filament wiring is different so they are not directly interchangeable.
Check both datasheets.

Yeah, I didn't know that ,and I have already fired it up. What did I do to the amp because of this ?

[g1]

They sent you the wrong tubes, contact them and get the right ones. Maybe someone thought they were ECC83's. The mojo kit is supposed to ship with 12AX7's.
You could rewire it to use the E88CC's, but then you need to use them all the time.
The nice thing about wiring it up for 12AX7's is you can try so many different tube types that use the same wiring but sound a bit different.

[gtrplayr1976]

I have contacted them. He tells me they don't even sell the E88CCs , So I have to send pictures of the boxes ,and tubes. Geez...

[J M Fahey]

I have contacted them. He tells me they don't even sell the E88CCs , So I have to send pictures of the boxes ,and tubes. Geez...

Can you link to the kit sellers site?

[gtrplayr1976]

Can you link to the kit sellers site?

British 18 Watt Style Head Amplifier Kit

[gtrplayr1976]

Would there be somewhere on here that might tell me how to check the bias on this amp ?

[J M Fahey]

Well, Mojotone is considered a "serious" company, but even themselves acknowledge in their assemby manual:

Packaging mistakes are rare for Mojo but
double check us before you start your build.

and this is clearly one of them.
If they bark at your "already having plugged the tube without asking" tell them you are no Tech, seeing "ECC something" made you think it was some 12AX7 equivalent and started asking in Forums "why doesn't my E88CC filament work" and that you expect them to send the proper tube, of course you will send the wrong tube back.

I think you will have no problem with it.

As of the Bias: congratulations, it's cathode/self biased so no adjustments

[gtrplayr1976]

Well, Mojotone is considered a "serious" company, but even themselves acknowledge in their assemby manual:

and this is clearly one of them.
If they bark at your "already having plugged the tube without asking" tell them you are no Tech, seeing "ECC something" made you think it was some 12AX7 equivalent and started asking in Forums "why doesn't my E88CC filament work" and that you expect them to send the proper tube, of course you will send the wrong tube back.















I think you will have no problem with it.

As of the Bias: congratulations, it's cathode/self biased so no adjustments

Oh don't worry I'll get it taken care of. I still have to send them pictures. I knew there was no adjustment for the bias. I just wanted to see what it was running at. ... Thanks for the help !

[J M Fahey]

I just wanted to see what it was running at.

As Enzo would say ... "Ohm's law *still* rules .... as well as all others"
To get tube (pair) current: measure voltage across cathode resistor (= to cathode to ground), divide by resistor value.
Then measure +B voltage, substract cathode voltage , and multiply by current you just found, will give dissipation for the tube pair in Watts.

Divide by 2, hoping both tubes are matched .

[gtrplayr1976]

Thank you. I will see if I can figure this out. By the way. I found some used 12AX7s ,and installed them last night. Amp fired up, seems to have a slight bit of hum with no input. I will be testing it tonight to see what it sounds like.

[J M Fahey]

I *bet* it's a *killer* sound .
Congratulations

[gtrplayr1976]

Thanks J M I sure hope it does. I should have changed the scheme to eliminate the tremolo ,and add TMB . I want to do that later. I never use tremolo. Maybe a master volume later. I'll just see how it sounds first.

[gtrplayr1976]

New tubes on the way. No charge of course