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@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@inbox.com>
> To: "BEHIELS JEAN-PIERRE" <ON4AEF@base.be>; <amps@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@base.be>
>>> Sent: Wednesday, January 19, 2011 12:18 AM
>>> To: <amps@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@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>
>>>>
>>>>
>>>> -----
>>>> No virus found in this message.
>>>> Checked by AVG - www.avg.com
>>>> Version: 10.0.1191 / Virus Database: 1435/3389 - Release Date:
01/18/11
>>>>
>>
>
_______________________________________________
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
|