The AM Forum

THE AM BULLETIN BOARD => Technical Forum => Topic started by: N0YXO on April 07, 2021, 06:48:16 PM



Title: EF Johnson TBolt
Post by: N0YXO on April 07, 2021, 06:48:16 PM
I have a Thunder bolt amp with a yl2gtm power rectifier board in it v1.o 4kv/5a. Can  any one give me any info on this product ?
not sure if it is installed correctly it was not finished installed  when I acquired the amp.   


Title: Re: EF Johnson TBolt
Post by: KA2PTE on April 07, 2021, 08:53:13 PM
Sounds like something to maybe replace the original HV diode tube rectifiers it had. Got any photos?


Title: Re: EF Johnson TBolt
Post by: N0YXO on April 07, 2021, 10:30:11 PM
That is what it replaces the hi voltage rectifying tubes and caps will post pic's tomorrow 


Title: Re: EF Johnson TBolt
Post by: N0YXO on April 08, 2021, 05:43:41 PM
This is the board


Title: Re: EF Johnson TBolt
Post by: W1NB on April 08, 2021, 07:27:01 PM
What is it that you need to know about it?


Title: Re: EF Johnson TBolt
Post by: N0YXO on April 08, 2021, 08:40:17 PM
Just trying to get some info on it after I drew out the schematic of it I understand how it works


Title: Re: EF Johnson TBolt
Post by: KA2PTE on April 08, 2021, 10:53:31 PM
Looks like (5) 450V caps in series for 2250V, then another set in parallel probably to filter the HV....and a string of diodes to I guess do the rectification.


Title: Re: EF Johnson TBolt
Post by: N0YXO on April 08, 2021, 11:10:03 PM
This is how it is wired


Title: Re: EF Johnson TBolt
Post by: MikeKE0ZUinkcmo on April 09, 2021, 06:52:46 AM
Looks like it should work fine, although there are twice as many capacitors as the original PS Schematic.


Title: Re: EF Johnson TBolt
Post by: w4bfs on April 09, 2021, 11:53:38 AM
the extra capacitors are there in case the HV bleeder goes open .... this is very conservative design


Title: Re: EF Johnson TBolt
Post by: MikeKE0ZUinkcmo on April 09, 2021, 05:19:25 PM
If ANY bleeder goes open all the other caps are going to bleed toward ZERO or to what ever leakage current the "open" cap goes to, just before it (probably) shorts from too much EMF.      

What value, and Voltage rating are the caps, something like 80-100F @450VDC?


Title: Re: EF Johnson TBolt
Post by: Detroit47 on April 10, 2021, 12:50:40 AM
Looks like it should work fine, although there are twice as many capacitors as the original PS Schematic.

There is only one 8uf filter cap on a stock T bolt. It has a choke input supply. Pretty funny.

N8QPC


Title: Re: EF Johnson TBolt
Post by: Pete, WA2CWA on April 10, 2021, 01:06:11 AM
Looks like it should work fine, although there are twice as many capacitors as the original PS Schematic.

There is only one 8uf filter cap on a stock T bolt. It has a choke input supply. Pretty funny.

N8QPC

There was two versions of the Thunderbolt with major changes in the HV supply. There were other minor changes between the two but for this thread, the discussion is HV power supply.
See attached



Title: Re: EF Johnson TBolt
Post by: w4bfs on April 10, 2021, 09:30:10 AM
Mike ... what I see from the photo are 470 uF @ 450V Nichicons ... I agree with what you say about equalizing res across each cap ... I was referring to overall HV bleed resistance which is fairly low value and high wattage ... can you say wump at turn on   ;D


Title: Re: EF Johnson TBolt
Post by: N0YXO on April 10, 2021, 02:43:15 PM
I have what appears to be the later one of the two models. I have installed in rush limiters in the path of the plate transformer the choke is in line with the caps I received no info of what was done with it the board has been modified from original configuration from what I can tell it was close to a Tbolt 2 power supply that I have acquired print of       


Title: Re: EF Johnson TBolt
Post by: WA1HZK on April 10, 2021, 04:56:37 PM
The one thing about those amps is that they were designed to use a CB set for a driver. Anything over around 3 watts is too much. Also, the power supply is very wimpy for those tubes. Under perfect conditions you can make 125 watts of AM but no more without losing your headroom.


Title: Re: EF Johnson TBolt
Post by: MikeKE0ZUinkcmo on April 11, 2021, 10:21:34 PM
As Carl mentions there were two distinct versions.  The second version up'd the capacity from 8uF to about 13uF, but47uF I'd say is far in excess of what's needed.   Mine still has the original 8uF Oil cap but before it goes on the ops bench again, it'll get the late model fix.



Title: Re: EF Johnson TBolt
Post by: Pete, WA2CWA on April 12, 2021, 12:22:05 AM
As Carl mentions there were two distinct versions.  The second version up'd the capacity from 8uF to about 13uF, but47uF I'd say is far in excess of what's needed.   Mine still has the original 8uF Oil cap but before it goes on the ops bench again, it'll get the late model fix.

Is Carl here?? ;D


Title: Re: EF Johnson TBolt
Post by: MikeKE0ZUinkcmo on April 12, 2021, 07:18:25 AM
Quote
...Is Carl here??  ;D...


CARL!! Who's Carl?  Carl's not here!! 

OOPS, Sorry Pete!!


Title: Re: EF Johnson TBolt
Post by: KA2PTE on July 17, 2021, 07:14:50 PM
In my travels I learned the last chassis made was a 1961-63 date and they upgraded R3 (350 ohms) to a non inductive array and did away with the cartridge style. Seems like its (3) 1K /14W values as per the pic.
Winds up being lower than 350 ohms (333) but I believe the grids of the 4-400A's wont mind ans perhaps some benefit attained.

The other revision is the addition of R118 (270K / 1w) which in the event the bias cable is not plugged in, provides the grids of the 4-400A's with some bias to keep them happy.


Title: Re: EF Johnson TBolt
Post by: Opcom on July 17, 2021, 09:38:00 PM
80-100mA bleed on the plate supply to get into the critical zone for the 5-25H swinger - very manly, very classic. That's what I'm talkin bout.


Title: Re: EF Johnson TBolt
Post by: KA2PTE on August 06, 2021, 08:43:59 AM
Well finally got my amp working really good after all the setbacks. Sept would have made it 3yrs
in the making. Learned alot, lots of helpful people here and on other sites made it possible.

I decided to create a support resource for the Viking Tube amps as some of them use similar parts
and they are becoming rarer all the time.

https://groups.io/g/johnson-tube-linears

I plan to post my journey there, and future plans, and hope more owners of those kind of tube amps join to make
it more fun.


Title: Re: EF Johnson TBolt
Post by: N0YXO on August 07, 2021, 08:00:59 PM
How do you post to the new group


Title: Re: EF Johnson TBolt
Post by: Pete, WA2CWA on August 08, 2021, 12:58:33 AM
How do you post to the new group

Got to sign up first to groups.io
https://groups.io/register
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands