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Old 27th Jun 2021, 1:04 pm   #61
FERNSEH
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Default Re: HMV 1920 made in 1960.

Hi John,
the best plan is remove the remote control receiver unit and test it on the bench. Change the valve to an ECL84 and use a separate power supplier.
Check that the 45Kc/s coils are peaked up and confirm that the unit is not going into oscillation. The setup notes do infer to the fact the unit is sensitive to HT voltage variations. "Check that HT voltage is correct, not too high or not too low as a result of mains tap setting or a receiver fault.

The HT voltage can be varied to find out how the relay reacts.
HKS wrote: "I can't believe anyone paying the price for this model would put up with all that madness. It must have worked OK at some time. John. "
In 1960 £150 was certainly a lot of money to pay for a TV set.

DFWB.
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Old 27th Jun 2021, 4:21 pm   #62
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Default Re: HMV 1920 made in 1960.

I thought of instability David. The valve must be conducting in a random manner to trigger the relay. Hum on the HT line?
The Philco 'Selectaflash' was very reliable. I serviced quite a few of these many years ago. Really great looking TV. I only encountered one 23" model. All the ones I serviced were the 1100 model. Good luck with it. I'm watching! Regards, John.
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Old 28th Jun 2021, 6:59 am   #63
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Default Re: HMV 1920 made in 1960.

David.

Maybe trying a zener or string of zener across C307 and adjusting R308 to suit? There appears to be little current drawn, maybe trying to get the HT stable at 165 - 170 Volts?

C307 seems very small at 1uF here as well. Fluctuating mains input voltage won’t help this circuit much!


Good luck.

SimonT.
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Old 28th Jun 2021, 10:11 am   #64
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Default Re: HMV 1920 made in 1960.

Hi Simon,
I've considered employing some means of stabilising the HT supply to the remote control receiver, even to the extent of making a separate power supply for it. Doing this could introduce a standby function instead of the mains switch-off system in use at the present time.
According to the service manual the HT voltage in the amplifier is 188V, but other conditions have to to considered such as the heater supply. It does seem the amplifier is sensitive to variations of mains voltage.

DFWB.
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Old 3rd Jul 2021, 10:52 am   #65
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Default Re: HMV 1920 made in 1960.

Yes, I saw this set on EBay too and even messaged the old-timer who was selling it; lovely old boy...but unfortunately he couldn't wait until I could sort transport to get it. Congratulations - it looks a super set!! I don't really have room for it anyway but then it's HMV...my weakness!
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Old 10th Jul 2021, 3:02 pm   #66
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Quote:
Originally Posted by thermionic View Post
David.
Maybe trying a zener or string of zener across C307 and adjusting R308 to suit? There appears to be little current drawn, maybe trying to get the HT stable at 165 - 170 Volts?
C307 seems very small at 1uF here as well. Fluctuating mains input voltage won’t help this circuit much!
Good luck.
SimonT.
How about this modification? A separate power supply for the remote control amplifier and another valve to drive the relay. The additional valve can be a 6C4 or one section of an ECC82. If an ECL84 can be found all the better, then a special 15volt heater winding on the "standby" transformer will not be required.
Apart from improving the stability of the remote control system a "standby" facility could be introduced, either to replace mains off, or, add another function to the single button remote control.
Possibly replace the mechanical handset with an electronic device.
Of course working within the rule which is only implement the tech of the times the set was made. No ICs or silicon transistors.

DFWB.
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Old 12th Jul 2021, 1:38 pm   #67
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Default Re: HMV 1920 made in 1960.

Hi David.

Your modification looks promising. Are you intending to use the existing relay? Not sure on the coil voltage, on the original diagram it seems to indicate that 5 Volts are dropped across it. Is this quiescent or activated state?

Looking forward to more progress 👍

Cheers.

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Old 12th Jul 2021, 2:46 pm   #68
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Default Re: HMV 1920 made in 1960.

Hi Simon,
to discover what's going on I'll connect up the 'scope to the anode of the triode section of the PCL84. I'll report back my findings later today.
Today, the remote control is working, but in a strange manner. Press the remote control button and the motor turns the tuner shaft to the next pre-set position. No problem so far. Press again and it moves to the next position, act fast and move on to the next position because this is switch "off". Press again for another pre-set TV channel. The next position is channel 1 but the motor continues to rotate to the next pre-set position after Ch1, it just bypasses Ch1 for some reason.
Very strange.
And yet channel 1 is easily selected from the push button on the front panel.

DFWB.

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Old 12th Jul 2021, 9:14 pm   #69
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Default Re: HMV 1920 made in 1960.

The resistance of the relay coil is 7000 ohms. The armature is activated when the current is 4mA.
The oscilloscope shows a 20 volt pulse at the anode of the triode. I think before any modifications are to be done to the remote control amplifier replace the relay first.
Try a retuned to 45Kc/s Bush Z718 remote control handset.

DFWB.
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Old 20th Jul 2021, 10:40 pm   #70
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Default Re: HMV 1920 made in 1960.

In fact jingling a bunch of keys works better than the remote control handset.
If an electronic handset is used it will be possible to extend the scope of the remote control system in this set. In the Rank-Bush-Murphy Z718 remote control system the single button remote handset allows channel changing and if the button is held down longer than three seconds the sound can be muted.

DFWB.
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Old 20th Jul 2021, 10:54 pm   #71
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Default Re: HMV 1920 made in 1960.

Beer can ring pulls and budgies spring to mind here David
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Old 21st Jul 2021, 7:56 pm   #72
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Default Re: HMV 1920 made in 1960.

Hi Baz you are right about budgies would make the Philips remote control G8 chance channel as well as a bunch of keys as well David kind regards Bob
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Old 24th Jul 2021, 9:38 pm   #73
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Default Re: HMV 1920 made in 1960.

Red to Black wrote: "Beer can ring pulls and budgies spring to mind here David "
Hi Baz, I forgot about that one and the G8 and G9 TVs with the simple pinger remote control handset.
Today, I found a good RBM Z918 single button ultra-sonic remote control handset.
Retuned 45Kc/s the handset works perfectly with the HMV. The longer duration signal provided the RBM handset accommodates some of the short comings of the remote control system.
Still convinced a separate power supply for the remote control receiver is desirable.

DFWB.
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Old 25th Jul 2021, 4:27 pm   #74
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Default Re: HMV 1920 made in 1960.

Attachment shows the channel pre-setting disc. Channels 7 and 12 were assigned to switching the set off. The selector disc is in the Channel 1 position.
With a separate power supply source for the remote control receiver, the "off" positions can then become standby. The power relay RL1 can be reactivated when the remote controller selects any TV channel position.

Did DER offer a rental TV set which employed this remote control system?

DFWB.
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Old 25th Jul 2021, 6:38 pm   #75
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Default Re: HMV 1920 made in 1960.

Hi Bob,
I was thinking Meccano.

DFWB.
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Old 25th Jul 2021, 6:54 pm   #76
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Default Re: HMV 1920 made in 1960.

Yes the chain is probably made by Renold the oldest established transmission chain company in the world kind regards Bob
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Old 5th Aug 2021, 12:31 pm   #77
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One essential item to replace is the channel indicator lamp. The remote control can switch the set off but to switch the set on again the on/channel button on the front control panel has to be pressed. The problem with this set is that after pressing the on/channel button the first position the channel indicator drum stops at is off so it has to be remembered to press the button twice in order to go past off, which is assigned to channel 12.
Changing the lamp isn't difficult.
From the 1961/62 R & T servicing book: "Remove the chain from the indicator drum sprocket and rotate the drum until the screw securing the it's right-hand end become accessible. Loosen the screw and withdraw the shaft slightly to free the end of the drum. The lampholder is mounted on a bracket at the left side of the drum, the bracket being secured to the chassis by two screws. If the screw at the rear is removed the right-hand end of the drum may be moved to the rear of the receiver, and the drum removed."
The replacement bulb should be a 15watt pygmy SBC type although the bulb in this set a one with a 25 watt rating.

DFWB.
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Old 5th Aug 2021, 1:24 pm   #78
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Default Re: HMV 1920 made in 1960.

Those drum drive components looked like they were made by Meccano.
The attached picture confirms the parts were indeed made by that firm.

DFWB.
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Old 5th Aug 2021, 7:56 pm   #79
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Default Re: HMV 1920 made in 1960.

Quote:
Originally Posted by FERNSEH View Post
Those drum drive components looked like they were made by Meccano.
The attached picture confirms the parts were indeed made by that firm.

DFWB.
I was thinking that looked like a modified Meccano sprocket and chain setup.
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Old 6th Aug 2021, 10:32 am   #80
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Might be a good idea introducing elsewhere in the forum a topic about the use of Meccano parts in radio and other other electronic equipment.

DFWB.
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