|
Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
|
Thread Tools |
17th Jun 2017, 9:28 am | #21 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
|
Re: How to adjust the IF transformers in a Philips 310A variant
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.
|
17th Jun 2017, 10:27 am | #22 |
Heptode
Join Date: Oct 2012
Location: London, UK.
Posts: 500
|
Re: How to adjust the IF transformers in a Philips 310A variant
|
18th Jun 2017, 10:19 pm | #23 | |
Tetrode
Join Date: Mar 2017
Location: Dublin, Ireland
Posts: 75
|
Re: How to adjust the IF transformers in a Philips 310A variant
Quote:
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)? |
|
18th Jun 2017, 10:42 pm | #24 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
|
Re: How to adjust the IF transformers in a Philips 310A variant
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.
|
25th Jun 2017, 1:35 pm | #25 |
Tetrode
Join Date: Mar 2017
Location: Dublin, Ireland
Posts: 75
|
Re: How to adjust the IF transformers in a Philips 310A variant
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? |
25th Jun 2017, 1:47 pm | #26 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
|
Re: How to adjust the IF transformers in a Philips 310A variant
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. |
25th Jun 2017, 5:59 pm | #27 |
Tetrode
Join Date: Mar 2017
Location: Dublin, Ireland
Posts: 75
|
Re: How to adjust the IF transformers in a Philips 310A variant
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! |
25th Jun 2017, 6:23 pm | #28 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
|
Re: How to adjust the IF transformers in a Philips 310A variant
If you haven't done so yet you need to check for the possibility of valve pin/socket contact problems first.
Lawrence. |
25th Jun 2017, 6:39 pm | #29 |
Tetrode
Join Date: Mar 2017
Location: Dublin, Ireland
Posts: 75
|
Re: How to adjust the IF transformers in a Philips 310A variant
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. |
25th Jun 2017, 6:43 pm | #30 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
|
Re: How to adjust the IF transformers in a Philips 310A variant
Contact cleaner should be ok on the valve holders.
Lawrence. |
9th Jul 2017, 1:06 pm | #31 |
Tetrode
Join Date: Mar 2017
Location: Dublin, Ireland
Posts: 75
|
Re: How to adjust the IF transformers in a Philips 310A variant
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. Last edited by MrVa1ve; 9th Jul 2017 at 1:18 pm. Reason: Added images |
7th Oct 2017, 6:46 pm | #32 |
Diode
Join Date: Sep 2017
Location: Dublin, Republic of Ireland.
Posts: 4
|
Re: How to adjust the IF transformers in a Philips 310A variant
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.
|
10th Oct 2017, 4:16 pm | #33 | |
Diode
Join Date: Sep 2017
Location: Dublin, Republic of Ireland.
Posts: 4
|
Re: How to adjust the IF transformers in a Philips 310A variant
Quote:
Badges available from here. |
|