Pye P125 Playboy record player rectifier

[john600601]

Hi all. I am changing the rectifier in a Pye Playboy record player but it has a kind I am not that familiar with as most of the record players I have use either a valve rectifier (live chassis) or rectifier with 2 terminals whereas the one in this player has 4, marked +, - and 2 ~ .
I understand a W08 rectifier is suitable and that the 2 connections from the transformer go to the two ~ (either way round), the - is to chassis, which just leaves the + connection which is where my query lies. The original rectifier has two connections on the +, a resistor (from the smoothing cap) and a wire from the other smoothing cap. Do I connect these exactly the same to the + of the new rectifier, or add another resistor in between (100 ohm 5w?). The record player is in practically mint condition so I want to be sure to do a thorough job on it. All resistors are within tolerance and I've replaced the two Hunts caps on sight. The cartridge is good. As it stands the player does work but I know having had these before a long time ago it should sound much better than it does. HT down. Thanks in advance.

[ben]

Originally Posted by john600601

Do I connect these exactly the same to the + of the new rectifier, or add another resistor in between (100 ohm 5w?)..

Why would you add another resistor there if there was not one before? Presumably you're swapping a faulty silicon bridge rectifier for another of same kind?

[john600601]

Thanks for the reply Ben, the original is a full wave selenium. Is the W08 a direct replacement? I can see the two wires from the transformer go to the two ~ (presume either way round) and the neg to chassis, I'm just confused with the + connection, as have read conflicting things on the internet, some saying add a resistor, and I'm not sure if this is correct or not? I am querying it as when I changed the rectifier on my Bush 31D I did add a resistor but admittedly was not an identical situation as I used just one 1n4007 diode (+ w/w/ resistor). Any help is appreciated. Thanks.

[Lucien Nunes]

The capacitor connected to the existing rectifier directly by a wire is the reservoir, which fills in the 'gaps' in the pulsating DC output of the rectifier for all the HT supply. The output transformer is fed with this voltage. The capacitor connected via a resistor is the smoother for the first two stages and the output valve screen. The capacitor and resistor form the smoothing to reduce the AC ripple significantly and the DC voltage somewhat.

The resistor you are adding is to compensate for the now missing internal resistance of the selenium rectifier, and should be connected directly in series with the silicon rectifier's positive output terminal. I.e. treat the resistor as part of the rectifier. Remove the two connections from the selenium's positive terminal (the reservoir and the smoothing resistor) keeping them joined togther, and connect them to the load side of the new resistor.

Adjust the resistor to achieve the correct HT voltage if you like, having ensured that the HT current is approximately correct (e.g. by checking the output valve's cathode voltage, as that also carries most of the current.)

[ben]

Ah, it's a selenium there originally. Take Lucien's advice!

[john600601]

Thanks both, I've ordered what I need and will report back once done.

[Edward Huggins]

The circuit for the Pye P125 is available above under "Service Data". You can see how the full-wave bridge rectifier is used. A good sounding record player, unusual as it is has a 3 stage SE amp. This was to allow generous feedback. Beware the tweeter which may have failed.

[Nickthedentist]

Originally Posted by Lucien Nunes

The resistor you are adding is to compensate for the now missing internal resistance of the selenium rectifier, and should be connected directly in series with the silicon rectifier's positive output terminal. I.e. treat the resistor as part of the rectifier. Remove the two connections from the selenium's positive terminal (the reservoir and the smoothing resistor) keeping them joined togther, and connect them to the load side of the new resistor.

Daft Q, I know, but presumably it's equally valid to have the R in series with the -ve bridge rectifier output terminal?

Similarly, could it be inserted in either of the ~ feeds too?

[john600601]

Thanks Edward, the tweeter is working. I have the service sheet, is there anything else to look out for on this model, as I know you are particularly familiar with it! The only two resistors that had drifted were the 220K now reading around 255K but according to the sheet they had a 20 percent tolerance so I haven't changed them, all others are near enough spot on. It's a fabulous design.

[Edward Huggins]

Do make sure the two inter-stage coupling caps have their correct values. If replacements are needed, you can replace with a slightly higher capacity to your advantage.

[ms660]

Originally Posted by Nickthedentist

Daft Q, I know, but presumably it's equally valid to have the R in series with the -ve bridge rectifier output terminal?

Similarly, could it be inserted in either of the ~ feeds too?

Yes, the resistor, diodes and reservoir capacitor form a series circuit so no problem, you could fit a suitable resistor in series with any of the rectifier's input and output terminals.

Lawrence.

[john600601]

Sorry for the delay with this, I have only just got round to doing it. I fitted the new W08 rectifier but whilst the performance was marginally better it is still nowhere near what I expect. At low volume it sounds OK but it seems to run out of puff at mid to high end volume and sounds rough, I would not say distorted but just not right, certainly not from this Pye model. I've had a couple of these before with no problems but this one is being a pain! I substituted both valves, no difference, changed cartridge, no difference (cartridge is an X5M, I tried another lower output one incase it was overloading - still sounded rough). So can rule out cartridge/stylus/valves. All resistors checked and changed if out of tolerance and Hunts caps changed. Aside from this, I have another query in that although I installed the W08 no problem, and added 100R 5W w/w resistor between the smoothing caps & the + connection of the rectifier as advised, after 10 mins I felt the smoothing can and it was VERY hot. Though no hum at all and no smell. Is the W08 not up to the job? Or could a faulty smoothing cap be causing the symptom described? I may just shelve it till I have more time, as don't want to get rid of it as the cabinet is near perfect, looks like it's barely been used. Thanks all.

[Station X]

If a smoothing capacitor gets VERY hot it's electrically leaky (behaves like a resistor) and needs changing. C5/C6.

[john600601]

Thanks, looks like they're the next job then, my main query in that respect was it anything to do with the new rectifier that could be causing the smoothing can to get hot or would that not be the case? Would failing smoothing caps cause deterioration in the overall sound (no hum, it's silent at minimum volume and only a light hum at max).

[Station X]

What sort of HT voltage are you seeing across C5 and C6?

[john600601]

I will recheck and let you know

[Edward Huggins]

This does sound like some kind of HT starvation. Measure the voltages in 3 places - just after the new rectifier, after the reservior cap and finally after the smoothing cap. The 3 stage amp in this will fully load the output tetrode.

[Richardgr]

Another option to lose a few volts is to add an inrush current limiter like a CL-90 on the on-off switch, and that steals a few volts as well as smoothing the startup.

[Lucien Nunes]

my main query in that respect was it anything to do with the new rectifier that could be causing the smoothing can to get hot

The old rectifier might have had high internal resistance for a while, resulting in reduced HT voltage. Electrolytic capacitors that have not been subjected to their normal working voltage tend to lose their ability to withstand it, as they become progressively unformed. A sudden return to full voltage or higher, can push them beyond what they will tolerate without first being reformed. It is also possible that the capacitor was responsible for damaging the original rectifier, if it had become unformed and presented a heavy overload when the player was first powered-up after long disuse.

[john600601]

Well the saga continues with this Pye I'm afraid, the smoothing can which I said was getting red hot was replaced and this improved things and it was working nicely. I fitted a BSR SC12M and it sounded very nice indeed, but then after a couple of days a new fault, an awful screeching/whistling, I've made a video here https://www.youtube.com/shorts/fzH5A0Lc5ek I rechecked the amplifier, so to confirm, all caps replaced, all resistors checked and within tolerance, I've resoldered every joint. Valves both changed for another set out of my spares box, valve bases sprayed with contact cleaner, volume and tone pots cleaned. I'm stumped now, any ideas please as I'm stumped! And yes I know the deck still needs work as you can hear in the video before the amp warms up! I'll get there eventually.. I hope!