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I removed old pics because of the part swaps above and below chassis. This is top pic showing new Roller, Tune & Load air variable. Progressively shorting rotary panel switch adds 120pF caps as needed for lower bands. Tune cap needs almost nothing. I'm seeing 300 mA zsac (2 NOS 4cx300a) while...

SBE base units had the fine walnut case, like furniture. Console was real pretty. The Sierra was my first base rig in 1974. They had a pcb mounted fuse that could only be accessed if radio removed from case. Console is real classic from that period. Miss that radio.

Yeah, I got it going now. :giggle: Apparently that protection diode made it impossible to set zsac/bias. 500 PO from 5w drive on 15mtrs AM from a pair of 4cx300a. That's enough to make me happy. Now I can finish setting the pi values for 40 & 80. neil

My 2nd post on this, I deleted the first, poorly written late at night. I'm chasing my tail lately on Tetrode project. It stopped amplifying despite correct voltages at tube pins and a reasonable zsac but in retrospect (below) I recognize the bias voltage was nowhere close to datasheet values...

I'm so tempted it's cross town so pick-up no problem. https://www.ebay.com/itm/395045335841?mkcid=1&mkrid=711-53200-19255-0&siteid=0&customid=link&campid=5336136228&toolid=20001&mkevt=1

True dat, but a tower that rotates got me all excited.

Entire tower rotates.

Thanks for posting those diagrams Nomad. Never a dull minute here it seems.

Been busy. In addition to the snubber diode, my inclination to use regular 12v zeners in place of BZX79C12 zeners was a bad idea. The BZX zeners (D-6 and D-118) control the mosfets that take the Screen & Plate offline when triggered. Also found BZX D-6, to be open/nc. After removing boards...

How did it go? I watched the YT vids and it looks useful. Cost is reasonable. Problem is, I've never used a real Spectrum Analyzer, so I have no experience to compare it to. Is it possible to use to view harmonic output from the freq of interest? For amps it would need a large attenuator but...

Thread was a great read. Kenrich Golden Eagle 750 was my first base amp early '90's.

Found the problem (ha I’ve written that before) : The diode across the coax relay (N4006) shorted. Keying amp repeatedly tripped the 3 relays upstream on the G2 board. Never saw an ordinary axial type diode go short. Removed G2 board and teste on table where it worked fine. I was oblivious...

Last Post for awhile. Relay repeatedly switch from On to Off fast when activated. I suspect the k-3 relay on the G-2 board is defective. I realize relays rarely fail ... don't think I've ever seen such a fail ... contacts get ruined but the coil armature mechanism? The G3SEK description for...

So I fell prey to NXP's fancy wording? It had me chasing my tail and I almost ordered another BZX out of reflex despite having a strip of 12v 1w zeners. Today I removed the relay board and found the problem, I think. It was mechanical: A torn pcb foil trace feeding the relay electrolytic...

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.