14/09/2025
Hi Folks
Well, as promised a little earlier, here’s my latest repair story. The Pye Model 806 was introduced in 1938 at the height of the boom in sets with Push-button tuning. Featuring full coverage of the Long, Medium and Short-wave bands, along with no less than six station pre-sets (for LW and MW stations) and four Tone-control pre-sets the specification of this set is somewhat impressive to say the least. However, this particular example is somewhat more complicated, as it has been quite heavily modified, (probably in the early 1960’s) as will soon become clear.
The original valve line-up of this set is TH4A (Frequency changer) TV4A (Magic Eye Tuning indicator) VP4B (Intermediate Frequency amplifier) TDD4 (Audio Amplifier) and PenB4 (Audio Output.) The rectifier is a DW4/350. But already this is where it gets complicated – Between the TH4A and the VP4B an additional plug-in I.F. coil has been added, with a valve socket to accommodate it (see photo 1) and an additional valve has been added – an extra TDD4. Additional modifications have included the addition of two rotary controls and a push button on the front (the two rotary controls appear to have once been wired one into the RF stage and one into the audio stage, but now are completely in-effective, the push-button switch is not connected to anything at all.) This has involved drilling holes in the front of the cabinet to accommodate them, which is a shame, but in fairness it looks to have been neatly and professionally done, and to a high standard at that. (See Photo 2)
So needless to say, quite a mystery going on here. You may recall that I restored one of these back in 2022 (see here for full details of that repair https://www.facebook.com/profile/100063285004857/search/?q=Pye%20806 ) however I was attracted to this one owing to the fact that my original 806 had an incorrect mains transformer fitted, making it prone to dangerous over-heating. In theory of course I could have had a new transformer built for it, but acquiring this set instead was undoubtedly a much cheaper (and simpler) option…. apart from all those modifications that is!
First job to do was to replace the mains lead as this was cracked and perished. I then powered up the set (the seller had mentioned that it was working, however it needed some attention as the sound was distorted) and sure enough it worked – some very slight distortion, but only very minor. The seller had suggested that this distortion may be due to an incorrect output valve having been fitted, however it actually turned out to be much simpler than that. (The output valve was in-fact the correct one after all.) An unusual feature of this set is the Expansion Indicator, which is a small 6.3-volt lamp, which is switched in and out of the audio circuit, by pressing the ‘Expansion’ button on the tone selectors section of the control panel. This brings the lamp into the audio tonal circuit, (in place of trader sheet marked Resistor 29, which provides negative feedback coupling when the Expansion lamp is not in use) thus creating sound expansion. In this case, however, the fitting had worked loose, causing the contacts of the lamp too short to chassis. Clearing this short, cured the distortion – and got the lamp working nicely – when the expansion button is pressed and the volume is turned up, it flickers in time to the speech and music, a pretty cool feature!
Following this, however, I observed another somewhat strange fault. I would have a station tuned in, (the pre-set buttons were also set up by this time – see photo 3 for a close up of these – note some of the station names and how the button of the selected station is illuminated!) when all of a sudden, the tracking would jump – each station would move up the dial by approx. 30 – 50 meters, and the push buttons would be thrown off tune. After a while, it would correct itself. This was eventually traced to a faulty capacitor (condenser) in the RF circuit – having sought advice on the issue I was able to trace the fault to a 0.002 uf Mica capacitor in the tuning section (on the Trader service sheet, this is C18 – Part Oscillator auto – circuit coupling) – even nudging it with the insulated end of a screw-driver would be enough to knock the fault on or off. Needless to say, this was promptly replaced.
Following this, however disaster struck – the magic eye that was in this set when supplied to me, was very dull, so naturally, I decided to replace it. I dug a replacement out (TV4A) which was a known good one and fitted it. Unfortunately, however I accidentally did the holding clasp up too tight the result being – you guessed it – the glass envelope cracked! A good Magic Eye valve completely ruined! After turning the air very blue I managed to search online (because of course I didn’t have another one going spare, now did I) and find a replacement for a good price, which thankfully worked. But an annoyance, nonetheless!
Then, it was a case of (once again) tuning in all the pre-set buttons. This is a case of using a screwdriver to tune in the corresponding coils and trimming condenser for each button. Each button covers a given section of the LW or MW bands, allowing up to a maximum of six stations to be tuned in. However, there was still a persisting problem – button six was only wanting to tune in ‘when it felt like it’ I tried repeatedly cleaning the contacts with WD40/contact cleaner – no joy. After much head-scratching, the mystery was eventually solved – and what a fluke – basically C17 (as listed on the trader sheet) is the fixed tracker for the MW Oscillator circuit, valued at 0.00055uf – this turned out to have an intermittent fault. So why was it only affecting one of the push-buttons you may ask? Completely by chance is the answer – it happened to be located right next to button six, and when button six was pressed, this would nudge it slightly, causing the fault to present itself. When one of the other buttons was pushed, it would be nudged back, causing the fault to clear! (Seriously, what are the chances??)
Needless to say, this condenser was replaced, the button tuned in, and the set is now performing nicely on all wavebands and all push buttons. – The first one I have tuned to Radio 4 LW (while it lasts) – the second one is blank, the third is tuned to Radio Caroline, the fourth tuned to Radio 5 Live (693 K/c’s, 433m) the fifth to Radio Five Live (909 K/c’s – 330 m) – Radio Five Live is of little use to me being that I am not a sports fan, however it was something to put on those buttons in an era when the MW is sadly becoming more and more devoid of stations. Finally, the sixth button is on my ‘pantry’ transmitter.
In future, I may fit a new frequency changer valve (TH4A) as the current one is prone to frequency drift, which of course can be annoying when using the pre-sets.
An additional job on this set was to wire a 160-ma fuse into the HT Supply. The idea/theory being that if a component short-circuits or overloads, the fuse will blow, thus removing any undue strain from the mains transformer. (A very expensive job if that burns out as any radio collector will know!)
But otherwise, a well performing set with coverage of every domestic frequency available at the time, some unusual features and four tone-pre-set buttons, which can be used in any combination. A pleasure to restore and to listen too. Hopefully the video will demonstrate this. – If you can excuse my appalling camera work that is!
Best wishes,
Chris