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It appears my thoughts of being near the end were premature. An on-board issue requires trouble-shooting beyond what I've done to date. I've been fortunate but I now need to take several steps back to address a rapidly chattering K-1 relay on the G-2 board, which precludes plate function...

Thanks for the Replies. The wording had me questioning everything and those tiny glass diodes look fragile. Handy Andy I did notice that missing line in the diagram symbol and I found myself attributing it to 'how the Scott's do it across the Sea' (G3SEK's plans). I've been wrestling with this...

I intended to replace a 1/2w BZX79-12 (NXP Semiconductor) with a 1N4742 generic (1w). They are both 12v. I've never seen the term Voltage Regulator Diode before. Datasheets seem similar but the diagram is not exactly the same. The BZX79 series are just Zener diodes, right?

This switch was a rare & good find. It has another pole that I can use the last 2-3 positions of. I found it confusing to keep the wires straight & short, started over several times. Almost ready to power On again, I had swap the roller for larger one, a few other changes. I signed in to...

Happy Day! Seller enclosed the original product enclosure from CRL! This switch is adjustable (somehow) and now I'd never seen that before.

Purchased a NOS CRL switch that required over a month of search & wait to find. There are so many CRL products sold online I assumed there must be datasheets somewhere. Radio Museum website reports the last company event was the purchase by Philips. It's hard to believe the company is Kaput...

I isolated the relay with it's own PSU and keeping the relay closed requires 75mA. PSU is scratch from a separate 24v transformer* feeding a small FWB and then a LM317 regulator module set for 22vdc**. Module heatsink gets almost hot. Placed near a fan now so it's workable. *...

Relays have occupied my recent free time. After seeing how slow it is for 1 relay to control another and maybe even a 3rd relay, I had to do something. In my online wanderings I found that in the case of NO, DC-coil relays that carry significant voltage or current, the opening is more of a...

I could not find and/or decipher the coil current requirement for this common 24v, Soviet relay. (datasheet in Russian). It's sold by several online vendors for as little as $30 plus shipping (>$10). The relay base is common to several configurations (SPST SPDT, etc). I found that the relay...

Not so fast. Trying to use old parts when I can. but the 24v relay is troublesome. Voltage Tripler is out, I'll spare the details, cap swaps, relay too big, etc. Ordered 24v transformer to power the V relay and a tiny low-current SP NO relay to control it. Putting the T. Boards back the way...

A real struggle to find a voltage source for vacuum relay (24v but it works with 14). I tried to increase the 12vdc HV trigger voltage (replaced the controlling 7812 with a 7815 and even the 12v zener on the 7812 Base with a 15v zener but nothing raised the voltage above 12. Eventually placed...

Could be an expen$ive proposition.

I have no experience with Vacuum switches. The Magnecraft reed-relay (SPST) I had between HVPS and plate choke began to stick. Thankfully, a safety habit of 'discharge before touching' paid off with only a frightful bang! Autopsy to look inside relay: 2 flat metal strips in a glass tube...

Thank you for suggesting a zener swap, I will do that in near future. The amp's personality improved a whole lot after the bias adjust. I'm using an old set of 300Y tubes now and they look burned & tarnished but they're giving me the best numbers I've seen yet. neil, NYC

My ex-wife still has my old tower. Went with the house decades ago. I did get the antenna though, lol.

Control grid voltage at -74 (as opposed to -70) working fine, I see no difference in PO. Plate current however, is noticeably lower. P.S. I'm going to close it up and stay with the -74 bias for awhile see how it goes. Maybe put the newer 300A's back in because I know those tubes better.

A tube swap reduced the difference between published bias voltage & zsac. Datasheet states -70v grid bias but to obtain a 200mA zsac I need to increase bias to -74v. So what should I follow? the published -70 with higher zsac or raise bias voltage to -74 for the lower zsac? These are all old...

Fine tuning homebrew grid-driven 2x 4cx300 amp. Plate current meter is accurate now :rolleyes:. Specified ZSAC for plate voltage 1500 and up is 100mA. With 2 tubes I should see 200mA. Bias voltage adjustment can reduce zsac by raising bias voltage for a zsac of 230mA which is still too high...