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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...

Kinda like a journal entry at this point but here goes another. Upon HVPS rebuild I found my plate current metering was faulty. I did not need a meter shunt. Stupid mistake # 173. Affects all prior plate current readings by making them too low, by a lot. Better late than never :rolleyes...

4cx300a amp w/ Tetrode boards: Awaiting delivery on new caps for HVPS. Going from 180uF to 330uF @ 450v Also scrapped the entire Tank circuit / band switch for a small La Pointe roller plus the separate Eldico 10M coil on the Tune side. The switch to FWB and new plate transformer increased...

Cannot escape Amps x Volts = Watts Need more Iron. Good lesson learned.

Amp seems happier with the FW bridge (instead of doubler) and new tranny (Heathkit 54-30 1800vac @ 400mA). Amp still on worktable and I must close it up & move it to operating location for more testing. Noticeably lighter without the 16A filament winding despite having 6 separate transformers...

Found it. I see the Rectifier & Cap boards currently listed on CTR are separate. EDIT: I got the HVPS board out today. I cannot justify not re-using it because it's just what I need and in great shape. I can also see that it's set for FWB if I add the remaining diodes. I had an extra 2...

It's been a few years since I made a doubler from the 1st board. If it's the same board, I'll strip the board down and reinstall diodes & caps. I attempted to find the board on your website but did not locate. Quality board thick plating that withstands re-soldering mistakes lol. CTR...