My manual says the idle current should be 4 amps...If not, to check
adjustment of R3 (bias adjustment)..If the idle current can not be set
to about 4 amps (.625 vdc on the bases of the 454's) if not then to
check the Q1/Q2 bias circuit operation...Let me know if you need more
info. I have the complete manual ( a photocopy, that cost me $65 from
Trans-world)..Sounds to me like an adjustment should do it for you, as
the amps seem to be working. Current should be 45 to 60 amps on voice peaks.
73's
Chuck
W6RD
North Pole wrote:
> I have a Trans World Electronics 500M with 8 Motorola MRF 454 transistor
> finals. I was playing around the other night with my K2 qrp rig keying about
> 8 or 9 watts into the amplifier. It amazed me how well it was working as I
> was getting an easy 100 plus watts and it seemed like I was still enjoying
> the qsk of the K2.
>
> Unfortunately, I put my hand on the heat sink and it was hot. Usually on ssb
> it hardly gets warm even with the occasional rag chew. I looked at the amp
> meter and the collector was drawing 20 amps with no rf input. I quickly shut
> things down. The next morning I popped the cover just to give a visual
> inspection. There is no apparent physical damage nor burnt odor.
>
> I put 50 or 60 watts of ssb rf into it last night and the amp easily put out
> over 500 watts drawing 70 amps on peaks. But,again, once the mike was keyed
> it drew 20 amps without any modulation.
>
> I am really not much of an electronics tech but open to any advice, comments
> or trouble shooting tips anyone may care to share. Or if there is a repair
> service that will work on a Metron. I hate to toss it out as I seldom need
> the 500 watts but its the only way I will get on 75 meters in the evening.
>
> Meanwhile back to cw qrp with the good old K2.
>
> Thanks for reading, Larry W8CCY
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|