[Amps] Fireing up a old Tl922 amplifier.

TexasRF at aol.com TexasRF at aol.com
Fri Jan 21 05:30:00 PST 2011


Hi Jean, there several ways to measure the 1A current flow. One method is  
to measure voltage drop across the 47 ohm resistor. If you are doing that 
with a  typical digital voltmeter it will display a value that is  
approximately .707 times the peak voltage. Since the filter capacitors are  charging 
only on ac peaks, you are not delivering power to a totally resistive  load. 
As a result, the waveform across the resistor will not be a sine wave and  
the voltage reading will be much higher than the rms value.
 
An accurate current reading will require use of an average reading ampere  
meter such as iron vane type. For your purposes an accurate reading is not  
needed.
 
If you are measuring voltage drop across the 47 ohm meter and seeing 47  
vac, then your reading is very similar to some I have taken with a 35 ohm  
resistor in the primary of a hv power supply. In my case, I was using the  
resistor to reduce the standby dc voltage to equal the full load voltage. 
 
If you can measure the dc voltage across each filter capacitor it will give 
 a good indication how they are forming. If one is much lower than others 
it  indicates leakage and perhaps needs more time to form or is defective. It 
could  also indicate the bleeder resistor has changed value and needs  
replacement. If a capacitor reads much higher than others it indicates  the 
bleeder resistor is defective and needs replacement.
 
73,
Gerald K5GW
 
 
 
 
 
In a message dated 1/21/2011 1:58:05 A.M. Central Standard Time,  
ON4AEF at base.be writes:


Hi;

Best wishes for you all for 2011.

I am quit  making my own start delay into a old (1988)TL922 amp.
I made two primary  transformer start up delays  for : A for filament 
supply.
B for HV sequencial 
start-up supply.

A  little explanation about my substantial modifications concerning the 
TL922  power supplys.
By powering-on I switch all ready a resistance of 10 ohm/50W  into the 
primary of the filament transformer circuit.
After about 3  minutes I switch on the HV tension with in series a 
resistance 
of  47ohm/50W by means of timer T1
I mean time I also swich-out the 10 ohm/50 W  of the primary of the 
filament 
transformer by means of that same timer  T1'
After 5 minutes I switch-out the 47 ohm/50W resistor of the primary of  the 
HV-supply transformer by means of timer T2.

This principle  works quit very well and it is very safely for the start-up 
life time of  the 3-500Z tubes ?
But I was a little bit scary about the cuurent (1A over  47 ohms is 47W 
!!!)witch flows of the HV-supply
without charge during  the 47 ohm/50W resistance was in circuit..
Just some bleeders resistances  over the HV-supply C's and over the whole 
supply as stabilisation of the  power HV-supply output.
I could not believe it was about 1A ???
That was  quit a good reason to ask some question around ?
Today I leave the whole  AMP under supply for a whole day nothing happens 
around.
May I conclude  everything is normal behind my old Tl922 ?

So a big story but I like to  now some others guys opinion and experiences 
around this  remarquable
consumption of the HV-supply and measurement I made around a TL  922.

73's Jean ON4AEF.





> ----- Original  Message ----- 
From: "Jim W7RY" <w7ry at inbox.com>
> To: "BEHIELS  JEAN-PIERRE" <ON4AEF at base.be>; <amps at contesting.com>
>>  Sent: Wednesday, January 19, 2011 4:20 PM
>> Subject: Re: [Amps]  Fireing up a old Tl922 amplifier.
>>
>>
>>> How  long is your delay? Should be no more than .5 second to 1  second.
>>>
>>> 73
>>> Jim  W7RY
>>>
>>>
>>>  --------------------------------------------------
>>> From:  "BEHIELS JEAN-PIERRE" <ON4AEF at base.be>
>>> Sent: Wednesday,  January 19, 2011 12:18 AM
>>> To:  <amps at contesting.com>
>>> Subject: [Amps] Fireing up a old  Tl922 amplifier.
>>>
>>>>  Hi,
>>>>
>>>> I am busy to fireing up a old  Kenwood TL922 amplifier(1985).
>>>> I have already build in a  start-up system for both filament and high
>>>> tension power  supplys by means of two homebrew timers,and a series 
>>>>  small
>>>> resistances in
>>>> de secundairys of  both transformers(filament 10 ohm-HV 47 ohm both 
>>>>  50W).
>>>> Both valves are not mounted(running with no charges  no consume).
>>>> By power-on the unit I saw that the  resistance of 47ohm/50W into the 
HV
>>>> supply is becoming  very hot.
>>>> I have made some measurements during start up  around this resistance 
>>>> and
>>>> measure 47  V over this resistance.
>>>> This means that the HV power  supply without charge consume 1A idling
>>>> current  !!!
>>>> Question is this normal ?
>>>> After  the timing sequence the resistance is normally pulling out of  
the
>>>> system and the supply runs like it must be I  suppose,nothing abnormal
>>>> happens further  !!
>>>> No overheating behind the amplifier box or whatever,no  smoke or 
burning
>>>> and heating  components.
>>>> Just the 10W bleeders over the capacitors warm  up a little (can easely
>>>> take my hand on it hi  )
>>>> I was wondering while this is so mutch or not  ?
>>>> Did I leave the amp a lot many hours under supplying  condition to the
>>>> give the HV-capacitors the time to  reforme after sutch long time(if 
>>>> this
>>>>  is the reason) ???
>>>> Could this last also a reason of the  fenomene ?
>>>> Or is 1A just normal standby current value for  this amp .....
>>>>
>>>> Regards Jean  ON4AEF.
>>>>
>>>>  _______________________________________________
>>>> Amps  mailing list
>>>> Amps at contesting.com
>>>>  http://lists.contesting.com/mailman/listinfo/amps
>>>>
>>>>
>>>>
>>>>  -----
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>>
>  

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