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Old 22nd Jul 2016, 2:42 pm   #1
pbengtech
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Join Date: Jan 2009
Location: Birmingham, West Midlands, UK.
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Default Marconi TF144H/4S low output above 2MHz

I have been reading the threads regarding TF 144 signal generators with ALC circuit problems with interest.
I have such a generator, that has not been used for some years.
So I thought it would be wise to carefully recommission it, in case I blew the thermocouple.
I reformed the supply caps, checked the turret insulation sleeves for leakage, and switched it on.
The 250v line was low, the generator worked but the output began to reduce as the frequency was adjusted above 2 MHz, until it was almost stopped at maximum frequency.
Changing the Black Hunts capacitors in the Ht power supply got the HT back to 250v, but although a lot of the accessible Hunts capacitors were leaky and were changed, nothing had any effect on the High frequency performance until I changed C130 a .001 hunts cap in the turret.
Now the output only changes slightly between min and max frequency.
Anyone want a working TF144? PS you know the neon is OK when it glows! It is not in circuit on all ranges however!
Phil
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Old 27th Jul 2016, 10:47 pm   #2
Phil G4SPZ
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Location: Bewdley, Worcestershire, UK.
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Default Re: Marconi TF144H/4S low output above 2MHz

Well done, Phil! I have a soft spot for these TF144s and spent many hours working on my own. However it now works well and is my generator of choice. And no, thanks, I don't want another...!
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