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Old 24th Apr 2017, 5:29 pm   #1
FERNSEH
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Default Pye D16 frame oscillator transformer.

That frame blocking oscillator found in the HMV 1804 has the sync pulse injection winding so should therefore be fitted in my Pye D16.
In order that the transformer can be fitted in the Pye an adaptor plate has been made.

DFWB.
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Old 26th Apr 2017, 4:34 pm   #2
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Default Re: Pye D16 frame oscillator transformer.

The blocking oscillator transformer has been wired into the circuit.
Initial results are not very encouraging, lack of height and no sound or vision.
At least the frame oscillator is running at the correct frequency.

DFWB.
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Old 26th Apr 2017, 5:37 pm   #3
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Default Re: Pye D16 frame oscillator transformer.

Get the box of capacitors out David. Fantastic performers the D16T but what a pig to work on! The twin chassis console is particularly nasty due to the short multi cables terminated with octal plugs and the alarming 6kv of mains derived EHT. Add to this the non insulated top cap on the anode of the HVR2 EHT rectifier and the smoothing cap mounted upside down with very accessible live connections just waiting to kill you when the chassis slips and traps your arm on your bench while testing. Take care. I have two of these landmark receivers but treat them with great respect. John.
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Old 26th Apr 2017, 6:29 pm   #4
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Default Re: Pye D16 frame oscillator transformer.

Hi John
The set I'm working on is the console version. To make servicing easier I'm thinking it might be a good idea to make up extension leads. An octal plug on one end and a socket on the other. The deadly power pack then can be kept well out of the way when carrying out any service work on the signals and timebase unit.
The other set needing more attention is the rarer Invicta console model.
As you say the pictures displayed on these sets are superb but they are little horrors when it come to doing any service work.
Those slider controls are nasty things.

DFWB.
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Old 27th Apr 2017, 3:47 pm   #5
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Default Re: Pye D16 frame oscillator transformer.

Hello All,

My D16 suffers from mild lack of height and I believe that the problem may well be the ECC34 Frame osc / output valve. I have a second valve (also well used) which doesn't exactly improve things !!

I believe that someone else was trying to find a possible replacement option, but I can't remember who.

Anyway, good luck with your set.


Alan.
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Old 27th Apr 2017, 5:19 pm   #6
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Default Re: Pye D16 frame oscillator transformer.

Hi Alan,
There is an American valve which might be a good replacement for the ECC34. The two sections of this double triode are dissimilar, one low power for the oscillator and the other is of much greater power for the output stage. When I return home I'll post up details of the valve.
Although the 6SN7GT works well in some sets as a frame oscillator and output, the Masteradio T852/1 for example, the 6SN7 doesn't work satisfactorily in the B16T.
From the Radiomuseum, Info for the ECC34: http://www.radiomuseum.org/tubes/tube_ecc34.html

I've just made up this extension lead to facilitate safe and easier servicing of the console versions of the B16. It's 600mm long, long enough to keep the power unit well out of way when servicing the timebase and receiver unit.
Two extension leads are required for the B16.

DFWB.
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Old 27th Apr 2017, 6:11 pm   #7
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Default Re: Pye D16 frame oscillator transformer.

I think that was me.

I have used a 6BL7GTA in my set with good results. It works out that Pye used (either inadvertently or not) the pin-out that is recommended for the two sections as oscillator and output. I suspect it was no coincidence though.
A 6BL7GT also worked perfectly should you happen to have one of those.

Pete
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Old 27th Apr 2017, 7:50 pm   #8
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Default Re: Pye D16 frame oscillator transformer.

6BL7GTA, that's the one I was trying to remember, also similar is the later B9A base version, the 6DR7.
From the Radiomuseum: http://www.radiomuseum.org/tubes/tube_6dr7.html
The 6BL7GT: http://www.radiomuseum.org/tubes/tube_6bl7gt.html
A circuit of an economical frame timebase accompanies the info about the 6bl7.

DFWB.
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Old 28th Apr 2017, 10:53 pm   #9
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Default Re: Pye D16 frame oscillator transformer.

The attachment shows the two extension leads connected to the Invicta TL37 or is it TL100? It's now possible to do some serious servicing on the timebases and receiver section of these sets.
Just one more item to make, an extension EHT lead.

DFWB.
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Old 3rd May 2017, 6:50 pm   #10
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Default Re: Pye D16 frame oscillator transformer.

The extension test leads are a success. It's now a much simpler matter to carry out any servicing work on these Pye and Invicta console receivers.
The intermittent line timebase failure in the Pye was traced to the drive trimmer C32A coming into contact with other components.
Repositioning the trimmer effected a cure.

DFWB.
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Old 4th May 2017, 11:08 pm   #11
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Default Re: Pye D16 frame oscillator transformer.

The frame hold is not very solid in this set and often needs resetting. The line hold is bit better but not by much.
When the other D16 chassis is repaired the effectiveness of the frame and line hold controls can be compared.

DFWB.
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Old 5th May 2017, 7:59 am   #12
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Default Re: Pye D16 frame oscillator transformer.

A lot safer David. You really have to take care with that 6kv mains derived EHT.
My two D16T's certainly have an unusual frame lock but once set in the mid position appear to hold OK. I would have expected a bit more certainty from Pye on such an excellent performer. John.
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Old 5th May 2017, 1:18 pm   #13
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Default Re: Pye D16 frame oscillator transformer.

The sync separator valve is supplied with only 50 volts from the resistor chain which comprises of the preset controls and two fixed resistors. In the Pye service manual these resistors are R30A to R43A.
So it follows that the maximum amplitude of the sync pulses at the anode of the valve will be less than 50 volts P - P. The valve is conductive only on the positive going sync tips, 90% of the duty cycle the valve is not conducting.
I'm considering modifying circuit so that the sync separator is supplied with a higher voltage, the "top" of the anode load resistor R26A and the screen grid could be connected to the junction of the height control and R31A. it's possible that 230volts might be too high so R31A could be replaced by two 15Kohm resistors and the sync separator connected to centre tap which would give approximately 140volts.
I will try out these modifications and report back my findings.

DFWB.
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Old 5th May 2017, 5:09 pm   #14
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Default Re: Pye D16 frame oscillator transformer.

Pursuant to my policy of Glasnost (openness) I have to report that the modification was unsuccessful. With further fiddling about with the circuits some improvement might have been possible but I have plenty other things do.
Raising the HT voltage supply to the sync separator did not increase the amplitude of the sync pulses and only result seen on the 'scope was that the negative going tips of the pulses were further away from ground potential.
This in turn prevented the interlace filter diodes from operating correctly.
Returning the sync separator to it's original condition revealed that sync pulses had an amplitude of only 25 volts P - P, a NOS EF50 was tried but there was no improvement.
However, another very simple modification can be tried. When the value of the anode load resistor R26A is increased to 18Kohms the sync pulse amplitude is raised to just over 40 volts P - P. Moreover, the sync tips are closer to ground potential, all the better.
By keeping the value anode load resistor low it's evident that the designer wished to preserve the shape of sync pulses. A high value load resistor will result in sync pulses having long rise and fall times. You saw the result of having a high value load resistor in Mkey's Pye V110.

DFWB.
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