You could try testing the filament current. ECC85 being 435mA isn't all that common.
I'm not familiar with your tester, but personally with my tester I'd retest as before (no more Vp) and slowly reduce the bias from where it was to see if that gets the current flowing, refering to the curves in the datasheet of what you suspect it to be to see if they're in the same ballpark. I worn tube will have less current but the mu/ curve spacing won't change that much.
I'm not familiar with your tester, but personally with my tester I'd retest as before (no more Vp) and slowly reduce the bias from where it was to see if that gets the current flowing, refering to the curves in the datasheet of what you suspect it to be to see if they're in the same ballpark. I worn tube will have less current but the mu/ curve spacing won't change that much.
All the Telefunken E283CC tubes I have seen on the net have a getter plate above the cage assembly - off of which the halo is supported. That is similar to the E88CCs, and the main reason I noticed these two mystery tubes were different.
Is the E283CC part of a family of tubes with similar pinouts which could have a Telefunken variant without such an arrangement that would appear more similar to my mystery tube?
I appreciate the pinout is what matters, but seeing something that matches exactly would inspire more confidence that I've properly identified the correct tube.
Thanks!
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@lcsaszar, it would appear the ECC808 / 6KX8 has the same pinouts as the E283CC, but more closely matches the architecture of my mystery tubes.
I set my TV-7D/U to the settings for a 6KX8, and voila, she passed with flying colors for both triodes. I plan to refit a two balanced, matched pair of Amperex ECC88's (not as robust as E88CC's, I know), and bring the preamp up on a variac. I'll test for HV on pins 3&8 just to confirm before fitting the now believed to be ECC808's.
Thank you all for their assistance, and I'll let ypu know what color the smoke is 😉.
-marcel
I set my TV-7D/U to the settings for a 6KX8, and voila, she passed with flying colors for both triodes. I plan to refit a two balanced, matched pair of Amperex ECC88's (not as robust as E88CC's, I know), and bring the preamp up on a variac. I'll test for HV on pins 3&8 just to confirm before fitting the now believed to be ECC808's.
Thank you all for their assistance, and I'll let ypu know what color the smoke is 😉.
-marcel
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No redesign taking place. I just acquired it and PO didn't have schematic nor knowledge of what the tubes were. It was in unknown condition, so I began by testing the tubes...4 were identical with E88CC labeling on them. I assumed all ro be the same, but two were were not (thus the scramble to identify).
Now that I believe I know what they are, I'll complete the testing, refresh as required, and pass on to my son with s recently completed ST70 for his new pad.
Thx
If I had to guess, the 808's were for the phono section since they seem to have similar specs as 12ax7's which are used often in phono pre sections. I guess I missunderstood your 88 plans. It seemed you were going to swap the positions of the ''mystery tubes...808's'' to 88's. Just me. Carry on. Glad you got the mystery knocked. Good detective work.