How to adjust the IF transformers in a Philips 310A variant

[PJL]

Measure the voltages on all pins of V2. This should tell you most of what you need to know about the condition. Is the valve heater lighting up? The cathode is disconnected in gram position but the voltage measurements should confirm if the switch is the problem.

[winston_1]

Originally Posted by MrVa1ve

I don't believe we ever had 220V although I'm no expert on Irish supply history.

The Irish republic voltage was 220 volts, UK mainland 240 volts, and NI 230 volts to take account of the fact that both UK and Irish appliances turned up there.

[MrVa1ve]

Originally Posted by PJL

Measure the voltages on all pins of V2. This should tell you most of what you need to know about the condition. Is the valve heater lighting up? The cathode is disconnected in gram position but the voltage measurements should confirm if the switch is the problem.

Apologies for the delay, much too nice a day to be stuck indoors! Anyway, I've measured all the pin voltages of the EAF42:

Heater(1,8): 5.6VAC
Anode(2):230V
Diode(3):-0.6V
g2(5):53V
g1(6):-0.8V

Pins 4 and 7 are grounded. The heater is lighting up, but this valve does not run hot. Even after several minutes it's the coolest valve in the lineup. I've done some tests and the gram switch is definitely working as it should. I'll double check my previous results, but I'm pretty sure the switch was in the radio position when I performed the test (fully counterclockwise).

The last time I checked, I couldn't find a signal at the junction of R7/R8 with the scope. Should I expect to see a signal at that point or is it an error to attempt a measurement there (i.e. AGC action)?

[PJL]

The voltages look OK but don't tell us much. G2 is about right but that is shared by V1 so the loss of V2 current might not have much effect.. You could try measuring V2 current by putting your meter on a mA range between chassis and V2 cathode and switch to gram input.

[MrVa1ve]

Some more updates. It turns out that most of my hunches up to now have been incorrect. The band select switch was faulty (bad contacts) which led me to believe that there was a fault in the receiver section. After a liberal dose of contact cleaner and some re-tests I'm pretty confident that the front-end section is working OK. It may still need some alignment (not IF!), but that's for later.

However, there's still a problem. Back at the start of the troubleshooting procedure, I fed an audio tone into the PU jack and got a response from the speaker. It turns out that the amplitude of my signal generator was cranked up quite high and even at that, the tone was audible but not ear splitting even at max volume. So, there seems to be an issue in the audio section and my suspicion is centred on the EBC41 (for now).

I've included an image that summarizes the test procedure along with measured resistances and voltages (DC and AC). I think the image is self explanatory. The bottom line is, having fed a 0.5V 1khz signal across R11 (input to EBC41), I'm getting practically no output across R16 (input to grid of EL41).

Note that I've replaced all the caps in the diagram and they are (or should be) at the values given in the datasheet.

Does the test look reasonable? Any obvious issues jumping out?

[ms660]

Your measurements suggest that the EBC41 might be low emission. If the heater is lit up ok I would be inclined to try another valve.

Lawrence.

[MrVa1ve]

Thanks Lawrence. Unfortunately, I don't have a spare EBC41. I do have a spare EL41, which I swapped in as a test and had no noticeable improvement. It does all seem to point to a faulty EBC41.

Does anyone have a spare EBC41 valve they'd like to sell? I'm also missing the rear cover (missing when purchased) and the Philips badge on the front (which seems to go missing on many of these units). If anyone has these items to sell, I'd be extremely grateful!

[ms660]

If you haven't done so yet you need to check for the possibility of valve pin/socket contact problems first.

Lawrence.

[MrVa1ve]

Actually, that was one of the first tests I did. I tested continuity by probing between the exposed pin tip and the solder tab and they all tested OK. I also lightly scraped any residue off the pins at some point.

Is it OK to use contact cleaner on the valve holders? If it is, I'll give that a try although I'm pretty convinced the contact is good.

[ms660]

Contact cleaner should be ok on the valve holders.

Lawrence.

[MrVa1ve]

It took a while, but my replacement EBC41 finally arrived. I put it in the set and... IT WORKS! Listening to RTE on LW at the moment (the other bands are surprisingly quiet here?) with a very satisfied look on my face.

To all who helped me get this working, a big big thankyou!

And once again, if anyone has a spare philips badge or a photocopy of the rear panel (another member has offered to make up a panel if I can send him a photocopy) then I would be very grateful.

[Paddy737]

The chassis scrubs up nicely. Is it a 310a or are you unsure on the exact model number. I have one with the same chassis but different cabinet, model BIF420a Irish built model.

[Paddy737]

Originally Posted by MrVa1ve

And once again, if anyone has a spare philips badge or a photocopy of the rear panel (another member has offered to make up a panel if I can send him a photocopy) then I would be very grateful.

http://www.bendijkman.nl/index.php/emblemen

Badges available from here.