Globe King 400/500 modulators interchangable?

[K8WBL]

Hello group, still working/cleaning a set of old GK400B and partial GK500A (deck and modded pwr supply)   the GK400B needs new coils, or at least a good rebuild of them as well as those finals...which I will probably use 5514 if I can get them to fit better....question..is the GK400 modulator directly interchangeable with the GK500A RF  decks.  In other words, I want to use the GK500A RF deck with the GK400B power supply and modulator....thanks.. Tim  K8WBL

[N3DRB The Derb]

hi Tim from another.

reminder of the stock finals an modulator tubes in each unit, please?

i dont know about the interconnects between the chassis, but should not be too hard to figger out.

[w3jn]

GK400= 5514s mudulating a pair a V-70Ds

[N3DRB The Derb]

if you have any problems there it will be in your mod deck driver stage prolly. I would think you'd need a tad more munky swing. Also, no way the modded impedence of teh v70's = 4-250, so the transformer taps will have to be played with a bit. I have no reference material here anymore, not even a arrl handbook so these are just guesses. Are they good guesses? I honestly dont know. I've lost a lot of knowledge I thinks.

[K8WBL]

Thanks, gonna have to get good copies of the schematics and compare.  The GK500A RF deck is in very good condition and ready to go, but missing modulator deck as someone used the RF deck as a Linear amp... previous owner stated that the power supply was "redone" - I see that the plate supply has been replaced and the 866A's were solid stated as well as a choke removed, caps added...I do have an Eico 730 modulator, but that would not be enough to modulate that 4-250 ... GK500 Mod used 811A's and the GK400 used 5514's (same tube, different filament - both high mu tubes)   Hoped WRL would have standardized the connections, will have to trace out but thought someone might just know the answer.

PS> looking for a pair of V-70D's -

thanks, Tim K8WBL

[Steve - WB3HUZ]

The weak link would be the mod tranny. If you only load the RF deck up to 350 watts input or so, you should be fine.

[N3DRB The Derb]

wouldnt the plate current be lower with the 4-250 for the same power level?

[K8WBL]

After listening to you guys I think that, even if its possible, its not advisable, besides I really dont want to break up the GK400 - but the RF deck needs all new coils, only have the 40 M ones so am looking for the 80 meters ones - got the xtals already...hope to get something going before xmas time....antennas today...73, thanks again to all..  Tim K8WBL

So as far as the GK500A I have w/o modulator, would I be better off simply trying to build one or find something surplus - I dont think my chances of finding another 500 series modulator will be realistic ...I have a Eico 730 modulator...too small?...

Tim

[k4kyv]

Have you thought about trying to wind your own set of  coils?

[N3DRB The Derb]

way too small. You could cathode modulate it with that eico.

[K8WBL]

Thanks Don, and others, will likely rewind my own...the smaller coils are broken up but the larger is in good shape....as far as using the Eico with the GK500 RF/Power decks....would rather just keep that with the Eico 720 transmitter and use them as a pair on AM until I get the GK going....so...will likely look into buiding my own modulator or find something large enough to work with the GK500 ..... as far as the GK400B is concerned, will get that going first....fix the coils, run 5514's in the final for now...maybe move or change  those neutralizing caps and HV choke to make room for the larger diameter 5514's ..... I cannot find out the Mu of the V-70-D or 812H ...but am assuming its a low or medium Mu....as opposed to the high Mu of the 5514's, 811'a, 812's or even teh 572B's (which would actually fix in the sockets well without moving the caps and chokes, at least the USA versions...the China 572B is fatter...getting close to getting some good on AM anyways...been listening to most of you guys on 3885...

73, Tim K8WBL

[w5omr]

....so...will likely look into buiding my own modulator or find something large enough to work with the GK500 .....

The difference in 5514's and 811's in infinitesimal. (you can't hear the diff) besides, 5514's are semi-rare.  811's are everywhere, and still cheap.