Thread: Pye 834
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Old 3rd May 2021, 9:21 pm   #1
cathoderay57
Octode
 
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 1,388
Default Pye 834

I bought this Pye 834 at auction. There don’t seem to be many of them about. The top of the cabinet had a large area covered in a black sticky substance which, fortunately, responded to vigorous rubbing with a cloth soaked in white spirit. There are some chipping and scratches but overall the cabinet is in nice condition for its age and all I plan to do is give it a coat of wax polish. When I opened up the back it was clear that some attempt at repair had been made, probably quite a long time ago, as witnessed by the presence of 3 x 16uF electrolytics dangling precariously from the speaker field coil terminals. The original smoothers would have been inside a cardboard box screwed to the baffle board to the right of the speaker. The speaker and HT wiring was rubber and had perished and crumbled badly. Somebody had wrapped it in yellow insulating tape but I removed the whole cable harness and made a new one from silicone rubber-insulated wire. I first checked the continuity of the AF output transformer and speaker field coil – OK. I also checked the dc resistance of the mains transformer primary and HT secondary – OK, or so I thought. Having replaced the rotted rubber cabling going to the on-off mains switch, luckily being able to pull through new wires inside the existing braided shield shell, I applied power. Oh dear, a sizzling sound and bubbling wax started erupting from the mains transformer. I had made a schoolboy error by measuring the dc resistance between the ends of the centre-tapped winding and chassis, where the centre tap is usually connected isn’t it? Well not in this case. Checking the circuit diagram showed that there is a pair of bias resistors in the earth return between chassis and centre tap. The presence of these resistors had given me a false indication that the HT windings were perhaps in better condition than they actually were. The mains transformer was toast (almost literally). Fortunately Ed Dinning came to the rescue with a suitable replacement – thanks Ed . Meanwhile I looked over the remainder of the set. I discovered that the tuning flywheel was made of Mazak alloy(aka monkey metal) and the casting had blown causing the flywheel to jam against the cross-bracket through which the tuning spindle passes. I started another thread on this with images here: https://www.vintage-radio.net/forum/...d.php?t=179102 but suffice to say I managed to file off material from the face of the flywheel such that it would rotate OK. Not perfect but good enough to use.
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