Tbone SCT 800 - Transformer Ratio ? & Mod Capsule with Rode HF6 !

[commanderberti]

hi does anybody know the ratio of the original SCT 800 mic transformer ? 12:1 ? or else? thanks

 

[cyrano]

According to this thread on this forum:

https://groupdiy.com/threads/3u-aud...-a-third-option-oem-mic-mods-to-47-251.77914/
It's 7:1.

 

[mhelin]

https://groupdiy.com/threads/tbone-sct-800-mod-apex460.47314/page-2#post-59968511.6:1

 

[commanderberti]

ok have now change the transformer with a UTM0512 (12:1) and the output are the same.. also i have change c8, put in a mullard tube AND: replace capsule to a : rode Rode HF6 - this mic now sounds fantastic and have a very low noise, high output and smoth high frequencis..

 

[83artem83]

Hi. I have a problem and maybe someone can tell me where to look for the breakdown: the microphone has lost sound completely. I just switched it on this morning, but there was no sound at all. No hissing, no whistling, no buzzing - no sound at all. Maybe someone has any ideas where to start looking for a problem with this sct 800?

my knowledge of electronics is not very much more, but I have checked the cables and they are fully functional) also tried installing a different capsule, which definitely works - nothing changed, no sound at all

what should I do?

 

[Khron]

Bias voltage not reaching the capsule?

 

[commanderberti]

Hi. I have a problem and maybe someone can tell me where to look for the breakdown: the microphone has lost sound completely. I just switched it on this morning, but there was no sound at all. No hissing, no whistling, no buzzing - no sound at all. Maybe someone has any ideas where to start looking for a problem with this sct 800?

my knowledge of electronics is not very much more, but I have checked the cables and they are fully functional) also tried installing a different capsule, which definitely works - nothing changed, no sound at all

what should I do?

is the tube ok?

 

[83artem83]

Sorry for the long silence and thanks to those who responded and helped.

I've been trying to find the cause of the microphone failure for a few days now, but my knowledge of electronics is nil, so it's been a long process.

In the end, the weak link was the microphone's regular lamp - this cheap Chinese lamp psvane 12ax7 simply stopped working, despite the fact that the microphone is new and has been working for no more than a month in gentle mode.

Honestly never thought that a new lamp could stop working))))).

thanks to everyone who responded to the call for help, thank you.

 

[Migs 31]

Sorry for the long silence and thanks to those who responded and helped.

I've been trying to find the cause of the microphone failure for a few days now, but my knowledge of electronics is nil, so it's been a long process.

In the end, the weak link was the microphone's regular lamp - this cheap Chinese lamp psvane 12ax7 simply stopped working, despite the fact that the microphone is new and has been working for no more than a month in gentle mode.

Honestly never thought that a new lamp could stop working))))).

thanks to everyone who responded to the call for help, thank you.

Same thing happened to me, on one of those T.Bone microphones.
The weak link, truly is that "el cheapo" 12ax7 valve/tube.
Beware of that and change it as soon as possible.
www.thomann.de have or had EH 6072/12ay7, 12ax7 and /or 12at7 in stock.

https://www.thomann.de/intl/electro_harmonix_12ay7_tube.htm
https://www.thomann.de/intl/electro_harmonix_tube_12_ax_7.htm
https://www.thomann.de/intl/sovtek_roehre_12at7.htm
M

 

[Nen'O]

ok have now change the transformer with a UTM0512 (12:1) and the output are the same.. also i have change c8, put in a mullard tube AND: replace capsule to a : rode Rode HF6 - this mic now sounds fantastic and have a very low noise, high output and smoth high frequencis..

Changing 2 Zener diode In psu (Z5,Z6) to 62V 1.3W will fix issue with high output and improve mics headroom significantly.

 

[Mauritius89]

ok have now change the transformer with a UTM0512 (12:1) and the output are the same.. also i have change c8, put in a mullard tube AND: replace capsule to a : rode Rode HF6 - this mic now sounds fantastic and have a very low noise, high output and smoth high frequencis..

What cap do you use for C8?

 

[commanderberti]

What cap do you use for C8?

 

[Mauritius89]

I've got caps from Wima (1uF, 400V) and they were way too big so I had to send them back. That's what I was looking for. Thank you!