1
\$\begingroup\$

I'm attempting to repair a Clarion C104 tube radio. I started the repair years ago, put it away, and now I'm giving it another attempt. When I started the repair, the transformer (Clarion part no. C80-223) was damaged, so I replaced it with an equivalent transformer (Hammond Manufacturing part no. 270DX). clarion transformer Hammond transformer Transformer windings

Unfortunately, several of the transformer wires have become disconnected between then and now, and I'm attempting to reconnect them correctly.

I understand that many tubes use a heater voltage of 6.3V--thus the 6.3V output on the Filament #2 winding. However, the Sam's PhotoFacts schematic for this radio seems to show the Filament #2 winding disconnected:

Sam's Schematic

I'm assuming that the lower winding in the schematic is Filament #1 since the 5Y3GT rectifier tube has a filament voltage of 5.0V: 5Y3GT Spec

Why does this radio leave the 6.3V tap disconnected?

In asking that question, I'm making assumptions. Perhaps these questions need to be answered first:

  • Am I correct in interpreting the stub on the upper tap of the transformer in the PhotoFacts schematic as indicating that it's disconnected?
  • Why did they ground the other leg of the upper tap if the entire tap is unused?
  • Why are there two loops on the 5.0 V tap in the PhotoFacts schematic and one loop on the 6.3 V tap? Shouldn't it be the other way around? Did I misinterpret which tap is which?
\$\endgroup\$
  • 7
    \$\begingroup\$ That looks like it might be an arrow-head on the end of that transformer tap, which I would be inclined to interpret as something along the lines of "we all know where this goes and we don't want to clutter up the schematic by drawing it in everywhere." \$\endgroup\$ – brhans May 7 at 15:05
  • 2
    \$\begingroup\$ @brhans Ah. OK. Looking at the schematic again, I see that pin 7 (one of the heater pins) on every other tube has no connection on the schematic. Perhaps it goes there. \$\endgroup\$ – watkipet May 7 at 15:09
  • 1
    \$\begingroup\$ And the wonderful old symbol for electrolytic condensers (capacitors) like components 7 and 8 in the rectifier section \$\endgroup\$ – Marla May 7 at 15:31
  • 2
    \$\begingroup\$ @StainlessSteelRat did you read brhans comment - valves (tubes) don't work without heaters! \$\endgroup\$ – Chu May 7 at 16:24
  • 2
    \$\begingroup\$ @StainlessSteelRat Heaters provide the electron cloud that's fundamental to tube operation, either directly or by heating a cathode, they are not optional. Omitting their connections on circuit diagrams was as commonplace as not showing the power supply lines on op-amp circuits today. \$\endgroup\$ – Chu May 7 at 16:45
6
\$\begingroup\$

That looks like it might be an arrow-head on the end of that transformer tap, which I would be inclined to interpret as something along the lines of "we all know where this goes and we don't want to clutter up the schematic by drawing it in everywhere."

So in this instance, I believe that you're intended to connect that tap on the transformer to all of the heater filaments.

\$\endgroup\$
  • \$\begingroup\$ Would it be safe to say that, "we all know this goes to the tube filaments", given that this is a schematic for a tube radio? Or is it better to leave that conclusion as an exercise for the reader of this question / answer? \$\endgroup\$ – watkipet May 7 at 21:17
  • \$\begingroup\$ Since every heater (OK except the rectifier) has one grounded pin and one unconnected, this is certainly the answer. \$\endgroup\$ – Brian Drummond May 7 at 21:19
  • \$\begingroup\$ @brhans I'll accept your answer either way, but do you think your answer would be better if you added that this is the heater connection for the rest of the tubes? \$\endgroup\$ – watkipet May 7 at 21:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.