pye p75a

[tiv48]

i am not shore about this one it is a bit of a mess (on first inspection) no valves being the first problem. under the chassis are signs that something has leaked maybe the original smoothing cap the rest looks untouched.
its been on the todo pile for ages and as i have a few days it is time to decide it and others fate (repair or strip for spares. i do like these pye sets ,so will check the transformers and make a decision
rob t

[Steve_P]

Not that bad. Have you got the valves from other sets that you could try. The valves are wired in Parallel on this by the way, so if one's heater goes O/C the rest stay up.

If you get an EZ40 and plug that in, you can check the LT and HT. Also if there is HT on the Anode pin of the EL41 (Pin 2) then this bodes well for the Output Transformer.

Good sets these. Get it fixed!

Cheers,

Steve P.

[tiv48]

hi steve its my intention to check the mains tx and the output tx. if no problems i will change the el41 grid coupling cap ,then fit a ez40 and run the set up from a variac next assuming lt/ht are ok will fit an el41 and check the audio stage .if after that it still looks good i will search my valve stocks for the rest.i tend to keep output and rec vales handy the rest are stored in hopefully marked boxes
and i did manage to find a uch42 for the feranti the other day.
thats the plan anyway.
i was allways taught to start with the power supply then audio and then work backwards and in this set this looks the only way to go..
rob t

[tiv48]

ok new mains mains lead fitted c19 and 20 (audio coupling caps) changed both were leaky
also found c23 (neg feedback) was very leaky so changed that.
found and fitted a nos ez41 ,now ready for first power on
rob t

[tiv48]

A bit more done to day smothing caps reformed.ez 41 fitted ,
time for some mains ,could not get at the variac so used lamp limiter fitted with 40 watt bulb avo conected across second 1/2 of smothing cap, voltage rose to 270 ,left for 15 mins nothing got hot or whent bang.
fitted el41 re applied power could not hear anything so checked volts allseamed ok!
connected signal injector to top of vol pot got a weak out put then did what i should of done and looked at the circuit ,there is of corse an audio pre amp stage in the ebc41 this is what the volume control feeds so fed the signal to c20 this couples the ebc 41 to the el41 ,now i have a nice loud output .
next i fitted an ebc41 i did not have a new one so had to dig the valve tester out and test some old one luck on my side the first one checked out good ,after fitting i now have the audio stage working well,decided to check c23 the tone corection cap as it was wax yes it was leaky
now to find more of the missing valves.
ps note the mains cable is fitted with a p clip also that c19 is hidden under c24.
pps i am working from trader sheet 1135.
rob t

[Geaney]

Looking good Rob, I've always been partial to PYE's though not many of them show up in my neck of the woods.

Cheers, John

[tiv48]

First cock up on this one going by the circuit i have i fitted the other valves ech42/ef41 the result was faint stations on mw only.
after spending far to long checking here and there i realised there was some thing wrong around valve 1.any of you who have worked on a p75a will know what the problem is.
yes valve 1 should be a 6c9 not a ech42 .
the trader sheet refers to model p75 not the 75a
does any one know of a substitute as i have scoured e bay and the is not one there.
rob t

[tiv48]

after serching i managed to find a 6c9 in a box of unsorted tv valves however this was not the end of my problems
the results were the same as the ech42 except the stations were in a different place.
as there was unexceptable hum i thought i would work on that first it was not there with only the ez41 and el41 fitted as i could not see fitting the missing valve causing it ,the only other thing i had done was to clean up some of the sticky mess under the chassis.
with the aid of a bright torch i found one end of c20 had come off.as i said it is hidden under c24 so iunsoldered c24 and replaced c20 with 4.7nf with longer legs .this should cure the hum.
i was amazed when powering it up to find the set now works fine.
as an experiment i swapped the 6c9 for a ech42 and it still works only difference is staitions not in the right place.
so as far as a pye p75a is cocerned either will do .
there is 1 hunts cap in the set but it checks out ok.
i am now left with the cabinet witch can join the feranti in anothe to do pile
more photos to follow
rob t

[Mark R]

Nice one Rob, it pays to check your work then.

cheers Mark

[tiv48]

well mark i remember the days when i used to get it right first time 90% of the time.
now i make mistakes would make a beginer blush.
this time this time it was me being lazy ,i had 4.7 nf cap on the bench witch had very short legs ,so i soldered it on to the cut leads of the original.it would have taken me less that 2 mins to get a new one.
rob t