I have an older 220 ten tec L network transmatch I am rebuilding, and I
notice that ten tec uses high voltage disk ceramic paddling caps in series
with the main tuning air paddler...
I notice that under some tuning conditions, the swr will drift and some of
the ceramic caps will get rather warm, even with barefoot power applied...
I am wondering if substuting the original ceramic caps with 2nF type caps
will stablized the swr drift.
----- Original Message -----
From: "Jason Cooper" <jbear45@msn.com>
To: <n5oe@nctwb.net>; "Discussion of Ten-Tec Equipment"
<tentec@contesting.com>
Sent: Saturday, July 21, 2007 3:18 PM
Subject: Re: [TenTec] Titan 425 troubles, R1 and blown 20a fuses
> If one capacitor went south, there is a very good possibility that some
> others were also very close to failure. You are doing the right thing by
> ordering some new ones. There is a possibility of a transformer failure,
> however, a Peter Dahl replacement is very expensive and you would have to
> replace the caps if you cannot test them at high voltage. I restored a
> 425 about 6 months ago and tested each capacitor with a variable HV power
> supply and an ammeter. After re-forming them, all my caps were well under
> 200uA at 500V so I did not replace them. If you can get to a HV supply or
> a HV curve tracer, you could test the caps and that would give you some
> reasonable input if the failure was caused by the caps. Also an ESR test
> is useful if you can find someone with an ESR meter. If I remember
> correctly, R1 (It's R2 on my schematic) is in the soft-start circuit and
> would certainly blow if one of the caps was drawing excess current.
>
> By the way, I just bought a whole lot of 2nF 10KV ceramic capacitors to
> replace the plate blocking caps (C6 and C7) These caps have the X5R
> dialectric and will drift very little with heat unlike the OEM caps that
> Ten-Tec used. This will fix the tuning drift problem on 80M and 160M. I
> would be willing to sell off the excess if there is any interest
>
> Good luck fixing your 425. Jason KN7AZ
>
>
> ----- Original Message -----
> From: Carlin Royal<mailto:n5oe@nctwb.net>
> To: tentec@contesting.com<mailto:tentec@contesting.com>
> Sent: Friday, July 20, 2007 2:45 PM
> Subject: [TenTec] Titan 425 troubles, R1 and blown 20a fuses
>
>
>
> I have a Ten Tec Titan 425 that I have only had myself for about 6 months
> now. The amp when I received it had 1 bad HV capacitor in the power
> supply. Due to lack of funds at the time I replaced the one known bad
> capacitor. A few months later I was operating the amplifier during a cw
> pileup for about 30 minutes, I set everything on standby and went to
> lunch. When I returned to the shack I find the amp had blown one of the
> 20amp fuses in the supply.
> After checking in the PS, I found that R1 the 10ohm 25watt wire wound
> resistor on the rectifier board had went open. I replaced the blown
> resistor and powered the amp back up, this time again blowing a 20ampfuse
> and the same resistor. Ten Tec advised to replace the original rectifer
> board with a new one, (82112 rev E I beleive) since they thought some
> diodes were probably leaking and was the cause of all my troubles. Now
> after replacing the old rectifier board with the new one from Ten TEc, I
> power the amp on and it blows another 20amp fuse but did not appear to fry
> the resistor this time. Here is the main question to the list; Could I
> have another bad capacitor that is failing under high voltage since they
> do not read any shorts on the VOM when individually beng tested. I have on
> order 8 new 400uf 450v caps from Newark Electronics and will be replacing
> them this week, but I am looking for more input as to the trouble. It just
> seems odd to me that when sitting idle for just
> 3
> 0 minutes the thing went south and now I have had all this trouble.
> Hopefully I am on the right track and it will be one of the caps in the
> PS, but would be interested to hear any other areas that I might could
> check within reason here on the very limited bench. Thanks for any
> advise/comments.
> 73
>
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