[Amps] Titan 425 power transformer question

[Pete Soper]

Hi Gerald,
   Bingo. The relay that should be shorting out the surge suppressor (on
only one 120v primary leg) wasn't pulling in because one or both of the
two 1000uf/35v caps on the rectifier board (C5 and C6) were holding the
coil voltage down. I replaced both and I have 2400v now.

Thanks!
Pete AD4L

On 06/06/2011 03:32 PM, TexasRF at aol.com wrote:
> Hi Pete, I suggest you do more testing before writing off the  transformer. 
> One failure scenario that would cause the described problem is a  surge 
> limiting circuit that is not shorting out the limiting resistor in the  primary 
> circuit.
>  
> If you measure the 240/120vac line voltage right at the plate transformer  
> primary, it should be quite steady during turn on.
>  
> If that checks ok, you can carefully do the same test on the transformer  
> secondary. It should also be quite steady at turn on.
>  
> Happy hunting!
>  
> 73,
> Gerald K5GW
>  
>  
>  
> In a message dated 6/6/2011 2:07:13 P.M. Central Daylight Time,  
> pete at soper.us writes:
> 
> Folks,
> A bug deposited a big glop of mud (+ larvae)  into the gap between one
> of the PS caps of my Titan and also glued the top  of the cap to the side
> of the power supply metal cover. The cover and the  rest of the case was
> very well grounded and the PS fuses never blew, the  amp just stopped
> working. I have no idea how long a mud/dirt short was in  place, but the
> larvae obviously didn't make it out alive.
> The cap  in question tested obviously bad and I made an exact
> replacement. All eight  caps now behave the same now, except the voltage
> across each varies by  1-5%.
> I spent a few days reforming the caps while fretting that  the
> transformer/rectifier by itself is only putting out about 1300 volts  in
> the "high" setting.
> With the caps in place there is only 1650  volts present (i.e. about
> 550 volts short of spec). If a 14 watt signal is  put into the amp
> briefly the plate voltage dives to about 1kv and comes  back to 1650 over
> the course of 3-4 seconds. All of the rectifiers are open  one way and
> dropping 1/2 volt the other way (with a meter having a diode  test 
> position).
> Am I correct to think the transformer is  toast?
> 
> Regards,
> Pete  AD4L
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