[Amps] TL-922 question

[Joe Subich, W4TV]

According to both the schematic in both the user manual and the 
service manual, there is no load fixed padder on 80 meters.  The 
loading capacitor is dual section - 770 pF and 1150 pF according 
to the service manual.  The second section is added on 80 and a 
pair of fixed 500 pF 3 KV (HV, type not given) caps added on 160. 

The TL-922 was known to have insufficient loading padders for 160 
as the JA "band" as at 1915 +/- 5KHz in the early days.  
 
However, without any fixed padders to be switched in on 80 meters 
and the unit "coming close" as it is, I would be double checking 
operation into a known 50 Ohm (dummy) load at 600 W output in the 
CW setting (rated 1 KW input) or 1200 Watts output with 50 WPM 
dits (rated 2000 PEP input) in the SSB setting to confirm proper 
operation.  

Attempting to drive a load other than 50 Ohms or run power above 
the design specifications for the amplifier can certainly result 
in "running out of room" on the loading cap. 

Having said all the above ... adding another 500 pF 3 KV cap 
(like C69, C70) across the 80 meter section of the loading cap 
just might get the amp "in range" for the operating conditions. 

73, 

   ... Joe, W4TV 
   



> -----Original Message-----
> From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On Behalf Of Robert B. Bonner
> Sent: Tuesday, August 29, 2006 12:10 PM
> To: amps at contesting.com
> Subject: Re: [Amps] TL-922 question
> 
> 
> Sorry I responded to this question last evening via my blackberry.
> Apparently it only sent the message to the original poster.
> 
> Just a little preview:
> I put myself through college in the 70's working at the Ham Dealer in
> Minneapolis as their tech.  It was a Collins, Drake, Yashmoo, 
> early Icoms
> ish, Ten-tec, Hallicrafters, Henry and KENWOOD dealer.  We 
> had everything.
> 
> I have seen this exact problem before.  While all the responses sound
> logical and everybody has figured out exactly why this 
> problem exists. (not
> enough padder) unless you'd seen this problem exactly before 
> you'd miss it
> and scratch your head. I had this happen on an almost new amplifier.
> 
> A loading control padder cap that is in common on both 80 and 
> 160 has opened
> up.  Because of the way the amp is built this unit is really 
> sandwiched into
> the amp.  There was no way to physically see the damage to 
> this unit until
> it was removed from the amplifier.  From the top it looks 
> like it is still
> in perfect shape.
> 
> While band switches fail, arc spark etc, usually they can be 
> wiggled for a
> time and get connection back.  When this thing pops its all over.
> 
> If I remember correctly the access for this was from the side, it took
> taking all the cabinet off.  It was more than 20 years ago I 
> fixed this. 
> 
> Also I think this firebox switched in a cap on 40 also, make 
> sure 40 is
> within reasonable range too as the fact that you can get 
> power out on 80 and
> 160 a small value has gone caput on you shifting the loader 
> to zero.  The 40
> cap might be the actual culprit.
> 
> Have at it. Dr. Bob K0DD
> 
> 
> 
> -----Original Message-----
> From: amps-bounces at contesting.com 
> [mailto:amps-bounces at contesting.com] On
> Behalf Of R L Measures
> Sent: Tuesday, August 29, 2006 5:48 AM
> To: Gudguyham at aol.com
> Cc: amps at contesting.com
> Subject: Re: [Amps] TL-922 question
> 
> 
> On Aug 29, 2006, at 3:27 AM, Gudguyham at aol.com wrote:
> 
> > In a message dated 8/29/2006 6:11:00 A.M. Eastern Standard Time,  
> > r at somis.org writes:
> >
> > In my experiences, they don't open, they short because the 
> dielectric
> > punches through.
> > Perhaps, but then will he still be able to load it up as he 
> says he  
> > does?
> 
>   If a Load C shorts, nothing gets through the tank.  Since there is  
> output, the switch that is in series with the Load C must be open.  .
> 
> > If it was shorted, then his variable load cap would be shorted to  
> > ground and he would probably not experience and change in loading  
> > due to it being shorted through the padder cap.  As he 
> explains it,  
> > it seems as though it may be opened.  Either way, the 
> problem could  
> > be with the padder cap.
> 
> I don't think this will be found to be the case.
> 
> 
> > Lou
> 
> R L MEASURES, AG6K. 805-386-3734
> r at somis.org
> 
> 
> 
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