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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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25th Sep 2021, 8:50 am | #1 |
Octode
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,241
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New project on the bench Pye P117
Hi all
It's that time of year when hopefully get to focus some time on my radios rather than outdoor activities. I picked this rather rough looking Pye P117 from my local vintage shop for £5.00. Definitely worth saving. The mains cable was joined to speaker wire and secured with tape. The gold surround had come off. The tuning knob was loose and has parted company with the chassis. Removing the chassis I've found lots of very poor repairs and badly soldered joints. My first question. There is a huge brown dropper resistor fitted across C49 and C50 live inputs. This is additionally to R28 which is located in its correct position. The rogue resistor is 1.8KR. The same value as the original R28 which looks to still be fitted in its original location. See photos. I could understand it if the original R28 has been removed! Please see photos. Any thoughts greatly appreciated. Please see photos Many thanks Dave |
25th Sep 2021, 8:55 am | #2 |
Octode
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,241
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Re: New project on the bench Pye P117
The original R28 which is the large green resistor about centre on the photo is marked up 2700r !
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25th Sep 2021, 10:12 am | #3 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: New project on the bench Pye P117
Well, the rogue resistor at 1.8K is drifting up as might be expected- it's marked as 1.5K. Since it appears to be a 10% part, it's also well out of spec, though probably not far enough to have much effect on performance
Possibly the humbucking part of the output transformer primary has gone open and the rogue is a bypass attempt or maybe a DPO found that it just reduced hum a bit. A low emission output valve or one affected by a leaky grid coupling C could unbalance the hum cancellation function.
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25th Sep 2021, 10:51 am | #4 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: New project on the bench Pye P117
Check to see if the hum cancelling winding on the sound output transformer is open circuit or not, according to the manual I'm looking at it should have a resistance of approx. 50 Ohms, it's the upper section of the primary as viewed in the schematic.
Lawrence. EDIT: Post crossed. Last edited by ms660; 25th Sep 2021 at 10:59 am. Reason: extra info |
25th Sep 2021, 6:36 pm | #5 |
Pentode
Join Date: Jul 2020
Location: Borehamwood, Hertfordshire, UK.
Posts: 216
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Re: New project on the bench Pye P117
Hi i have two of these i have restored the cabinets and Electronics spent most of a week on both i am very happy with the results they look great and perform well on all three wave bands TAB
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26th Sep 2021, 7:41 am | #6 |
Octode
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,241
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Re: New project on the bench Pye P117
I've tested the humbucking part of the output transformer. I disconnected the wires and I have a reading of 42 ohms. The trader sheet states 50 ohms, with a difference in meters used, mine being a DMM I would say this is ok. I then snipped the original R28 out (well the one soldered in the correct place). This is either open circuit or drifted so high in value my meter is unable to read it. Hence why the other rogue resistor is fitted directly under c49 and c50. They simply left the old resistor in circuit and bypassed it with a new one.
Strangely the open circuit r28 doesn't appear to have got hot and burned out. Also its been replaced before as its of the incorrect value 2700 ohms instead of 1800 ohms. |
26th Sep 2021, 8:53 am | #7 |
Octode
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,241
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Re: New project on the bench Pye P117
One other question, does anybody know the total set current draw approximately of this set. I'd like to calculate the wattage resistor required to replace R28. I obviously can't plug this in and measure that at the moment. Neither is it quoted in the service data. Many thanks
Dave. |
26th Sep 2021, 11:28 am | #8 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: New project on the bench Pye P117
In the manufacturer's data, it's quoted as 2,000R, 6W.
Trader cites 1,800R. It carries about 30mA dc but will also have some superimposed ripple current. It doesn't have to handle the output stage anode current. Trader lists all the anode and screen currents in its valve table.
__________________
....__________ ....|____||__|__\_____ .=.| _---\__|__|_---_|. .........O..Chris....O |
5th Oct 2021, 11:05 am | #9 |
Octode
Join Date: May 2011
Location: Bromyard, Herefordshire, UK.
Posts: 1,241
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Re: New project on the bench Pye P117
Good morning, not much progress to report as I'm away in Northumberland this week on holiday. However just before I left the resistor landed on the door mat. 1800 ohms, 7 watt. This will hopefully sort out the shenanigans of the R28 issue where the original was open circuit or gone too high to measure. Then some replaced it with a resistor straight across the c49 and c50 but leaving the original still in place! This confused me thinking someone had added in additional dropper/ smoothing. Get this fitted on return from holiday and a gentle audio coupling re cap . A voltage check on all valve bases to make sure all is well and no hidden nasties and all should be good.
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