JTM45 / 50 Build

Help Support GroupDIY:

Spencerleehorton

Well-known member
Joined
May 12, 2012
Messages
3,251
Location
Felixstowe, Suffolk, UK
I've got no idea what's in them, might cut one of mine open and see!!

Meanwhile, back to the build!!
Have made my own dual cap sockets and mounted them, the iec is installed along with the octal sockets and one 9 pin socket, have to order some more.
Have offered up the turret board to see where I need to mount it.
Pots I've put in along with fuse holders.
Head cabinet I routed edges and gave it a sand, will order tolex at end of the month and hopefully next month this should be all finished and operational!!
 

Attachments

  • 20210324_160908.jpg
    20210324_160908.jpg
    224.3 KB · Views: 28

Spencerleehorton

Well-known member
Joined
May 12, 2012
Messages
3,251
Location
Felixstowe, Suffolk, UK
Few more bits and pieces came in the post today but gonna have to wait 2 - 4 weeks for txf.
Hopefully can get everything ready for them.
I'm interested in buying a variac, they seem to have some on ebay and alibaba, it's a red one with a digital readout, anyone had any experience with these?
 

Spencerleehorton

Well-known member
Joined
May 12, 2012
Messages
3,251
Location
Felixstowe, Suffolk, UK
Transformers are arriving today!!

still need to do faceplates and piping and quite a few other bits to tidy this up, but its definetly getting there now!
 

Attachments

  • 179290901_1639452742931821_1191093647848626794_n.jpg
    179290901_1639452742931821_1191093647848626794_n.jpg
    291.2 KB · Views: 12

Spencerleehorton

Well-known member
Joined
May 12, 2012
Messages
3,251
Location
Felixstowe, Suffolk, UK
just powered this up and getting 260vdc at the A point after the diodes
getting 28v at the 220k neg bias point and 25v at the next diode.
getting 328v at the lower 8.2k 2W and 290vdc at the top 8.2k 2W

All voltages seem low?

When i then turn on standyby all voltages drop!!??

As always something weird is going on!!
 

Spencerleehorton

Well-known member
Joined
May 12, 2012
Messages
3,251
Location
Felixstowe, Suffolk, UK
I keep forgeting to unplug my current limiter!! doh!!

Getting good voltages throughout so far, need to check the heaters and cathodes, but B+ voltages start at 446v, 343v, 290v, 270v.

The main problem is no output, but they did send me a transformer without the 4ohm winding so i need to find out the colour code and see what is what.
 

Spencerleehorton

Well-known member
Joined
May 12, 2012
Messages
3,251
Location
Felixstowe, Suffolk, UK
Well that didnt seem to be the problem, the heater voltages is only at 5.8v so something is up?
I'm gonna take the tubes out and take the voltages again and see what's off.
 

Spencerleehorton

Well-known member
Joined
May 12, 2012
Messages
3,251
Location
Felixstowe, Suffolk, UK
Hopefully today get to the bottom of what's wrong, I think the output txf needs switching on the primaries as the output txf let out a big screech!! I spotted I had the 1M and 470R switched so that's why no output!!
Still dont know why the heater voltage is only 5.9vac without tubes?
 

Attachments

  • 20210505_211641.jpg
    20210505_211641.jpg
    185.8 KB · Views: 10

john12ax7

Well-known member
Joined
Oct 14, 2010
Messages
1,851
Location
California, US
Have you checked your wall voltage? And also are you on the right tap of the transformer? There would also be a tolerance on the transformer.
 

Spencerleehorton

Well-known member
Joined
May 12, 2012
Messages
3,251
Location
Felixstowe, Suffolk, UK
yes im definetly on the right tap, they wound the 2 x 3.15vac CT with 2 x grey and violet for the CT.
CT is to GND and ive attached the grey leads to the filament connections on the tube sockets.
 
Top