Bigman80
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Post by Bigman80 on May 28, 2020 16:37:28 GMT
Ok thought I'd have another play and decided to change out the 7805 just in case but then on switch on I think in messing I've shorted it and ****** it up so need to take it out again. This board won't be worth a light soon... :-) Oh no!!! |
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Post by Deleted on May 28, 2020 17:32:00 GMT
Don't know how but think I killed the 2.7v zener so changed that too and we're back to the correct voltage across it but only with no valves installed....
It's in danger of being launched at the minute....
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Bigman80
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Post by Bigman80 on May 28, 2020 17:40:14 GMT
Don't know how but think I killed the 2.7v zener so changed that too and we're back to the correct voltage across it but only with no valves installed.... It's in danger of being launched at the minute.... This is very strange... Are your valves ok? |
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Post by Deleted on May 28, 2020 17:45:15 GMT
I hope so.... Yesterday I could get V1 and V2 glowing and swapping the two 7DJ8s in V1 position gave the same result. Adding the second 7DJ8 into V3 dropped them all.
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Bigman80
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Post by Bigman80 on May 28, 2020 18:00:25 GMT
I hope so.... Yesterday I could get V1 and V2 glowing and swapping the two 7DJ8s in V1 position gave the same result. Adding the second 7DJ8 into V3 dropped them all. Dont they have a heater voltage of 6.3v vs the PCC88 7v? Could that be a problem? I know folks have used a 189 in place of one PCC88 |
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Post by Deleted on May 28, 2020 18:06:44 GMT
Yeah probably don't recall offhand but heater voltage is 7.7v. 5v of the 7805 plus the 2.7v of the zener...
Anyway, as I'd forgotten which was which I just tried again and one of the (I'll change the name lol) PCC88s might be duff. With the other one in place and the 12ax7 I can get V1 and V2 glowing
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Bigman80
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Post by Bigman80 on May 28, 2020 19:50:40 GMT
Yeah probably don't recall offhand but heater voltage is 7.7v. 5v of the 7805 plus the 2.7v of the zener... Anyway, as I'd forgotten which was which I just tried again and one of the (I'll change the name lol) PCC88s might be duff. With the other one in place and the 12ax7 I can get V1 and V2 glowing Lol....thanks Ok, so a duff valve may explain it |
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Post by Deleted on May 28, 2020 20:14:20 GMT
It’s possible although I did get them all glowing yesterday, not at the same time, but glowing regardless. Not the case today so maybe it was on its way out. I’ve sent Watford a mail and I’ll see what happens about getting it replaced.
Fun and games.......
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Bigman80
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Post by Bigman80 on May 28, 2020 20:26:43 GMT
It’s possible although I did get them all glowing yesterday, not at the same time, but glowing regardless. Not the case today so maybe it was on its way out. I’ve sent Watford a mail and I’ll see what happens about getting it replaced. Fun and games....... What a pain. |
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Post by Deleted on May 29, 2020 15:59:49 GMT
Ok how about this one. I have just noticed that after a long switch off (I tried it this morning) it doesn't fire up at all with valves in V1 and V2. If I remove V2, V1 fires up. I can then replace V2 and that will come up too now. Leave it off a while (don't know how long) and then repeat, V1 and V2 don't fire up together until V2 is removed initially.
Any clues?
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Post by Deleted on May 29, 2020 16:21:06 GMT
Check you are not exceeding the heater current. The reg may fire up if it is within spec with 2 valves and go into shutdown with 3.
I dont know what valves you have in there, but if the reg is specced for a certain current, stick to it. eg an ecc 83 (I dont know what it uses this is just an example) requires 300ma, so 3 makes 900ma heater current,set the reg to pull 1a max. swapping in a set of something else that requires 400ma apiece makes 1200 total so the reg doesn't like it one bit. exceeding it might trigger it to shut off.
Check also for a short to earth on the valve heater pins of the valve that keeps tripping it out, that would also trigger it to shut off
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Post by firebottle on May 29, 2020 16:31:50 GMT
Scotty what valves are you using? Oli thought it was 7DJ8 which even though some sites state they are equivalent to PCC88's they are not.
A true PCC88 has 7.6V heaters and the 7DJ8 has 7V heaters. I think you need to reduce your heater voltage to enable the regulator to start up properly.
Replace the 2.7V zener with an approx 2V drop, I suggest 3x diodes in series (connected the opposite polarity to the marked zener).
You will need to reduce the paralleled 8.2 ohms that feeds the ECC83 with 2.3 ohms. A 2.2 should be close enough.
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Post by Deleted on May 29, 2020 16:46:25 GMT
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Post by firebottle on May 29, 2020 17:25:52 GMT
I'll still stand by what I say, 7DJ8 does not equal PCC88.
Try lowering the voltage.
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Post by Deleted on May 29, 2020 18:59:54 GMT
Yeah I will try it. Tbh I didn’t really read the description I just ordered them. Pretty sure I saw a link on here for them, intrigued now.....
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Bigman80
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Post by Bigman80 on May 29, 2020 19:13:43 GMT
Yeah I will try it. Tbh I didn’t really read the description I just ordered them. Pretty sure I saw a link on here for them, intrigued now..... They are cheap enough for testing with. |
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Post by Deleted on May 29, 2020 19:27:34 GMT
Yep good shout, thought about having a look round rather than bodging diodes in and cobbling resistors together lol
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Post by Deleted on May 30, 2020 6:36:45 GMT
I'll still stand by what I say, 7DJ8 does not equal PCC88. Try lowering the voltage. Just a note but probably worth taking 7dj8 out of the BOM if it really can't be used to save anyone else getting them. |
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Bigman80
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Post by Bigman80 on May 30, 2020 7:27:11 GMT
I'll still stand by what I say, 7DJ8 does not equal PCC88. Try lowering the voltage. Just a note but probably worth taking 7dj8 out of the BOM if it really can't be used to save anyone else getting them. Removed and I have no idea why they are in there. EDIT: Just to add, i just realised that the links to the BOM (earlier ones) allowed edits, so i am presuming they (& 12aX7) were added by our american Friends. That said, i am looking though the experiences of others and there are people using them?? How puzzling. |
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Post by firebottle on May 30, 2020 8:03:17 GMT
Scott can I ask you to try something. Can you connect an 8.2V 5W zener across the input and output of the 7805 with the cathode (stripe) connected to the input.
I have one, a 1N5344B, that I can send to you.
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Post by Deleted on May 30, 2020 8:09:50 GMT
yep sure no probs at all.
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Post by Deleted on Jun 1, 2020 12:11:32 GMT
okey dokey can someone please tell me exactly what valves they have in use? Looking at PCC88 specs suggest a 7v heater, some places say 7.6v yet every ebay seller I have asked are unable to give me that information.
There's a reasonable chance that no matter how cheap they are I am buying more of the same (voltage wise) so I may as well copy folk that have working valves.
Thanks in advance!
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Post by jimbo on Jun 1, 2020 12:40:35 GMT
Tubemonger go some matched pairs of Tungsram PCC88 for sale today. $65. 1971 NOS look tasty.
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Post by Deleted on Jun 1, 2020 12:52:36 GMT
Tubemonger go some matched pairs of Tungsram PCC88 for sale today. $65. 1971 NOS look tasty. Thanks but I want to buy exactly what someone else has and is working.
I have already fallen foul of is it a PC88, is it a 7DJ8, does it run on 7.6v, should it run on 7.6v etc etc so don't want to "risk" it again lol.
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Post by jimbo on Jun 1, 2020 13:01:55 GMT
Tubemonger go some matched pairs of Tungsram PCC88 for sale today. $65. 1971 NOS look tasty. Thanks but I want to buy exactly what someone else has and is working.
I have already fallen foul of is it a PC88, is it a 7DJ8, does it run on 7.6v, should it run on 7.6v etc etc so don't want to "risk" it again lol.
Ah I understand. |
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Deleted
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Post by Deleted on Jun 1, 2020 13:05:43 GMT
Can't you simply give yours to someone else for them to try in their's?
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Post by Deleted on Jun 1, 2020 13:19:40 GMT
Yeah I could I guess but Alan seems to think the issue is that mine have 7v heater requirements versus the 7.7 the phono stage puts out.
The issue is I can find specs showing PCC88 is 7v as well as 7.6v so I have no idea what I'll get if I buy something. I must be missing something as otherwise every man and his dog would find these issues. Maybe there is something else wrong with my stage which I guess borrowing someone's working valves would prove. I am happy to prove that myself but only by buying 100%, guaranteed, never to be repeated, get 'em while you can PCC88 valves :-)
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Post by firebottle on Jun 1, 2020 13:27:15 GMT
Hi Martin,
I have sent the 8.2V zener and a 1 ohm resistor in the post this morning for you to try.
I use a Telefunken PCC88, a russian 6N2P-EV and a Matsushita 7DJ8/PCC88.
The Matsushita heater does look a little brighter than the other 2. I have just been looking at all the data sheets, La Radiotechnique, Philips, and Tesla show a heater for PCC88 of 7V. Another Philips data sheet shows 7.6V which is the one I have based the design on.
Telefunken valves made by Siemens are quoted as 7V heater. I am bloody confused myself now.
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Post by Deleted on Jun 1, 2020 13:28:27 GMT
I appreciate what you're saying. But if you gave your's to someone else to try - you would know - one way or the other - where the problem lay, and save forking out for further valves you may not need.
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Post by Deleted on Jun 1, 2020 14:09:46 GMT
Hi Martin, I have sent the 8.2V zener and a 1 ohm resistor in the post this morning for you to try. I use a Telefunken PCC88, a russian 6N2P-EV and a Matsushita 7DJ8/PCC88. The Matsushita heater does look a little brighter than the other 2. I have just been looking at all the data sheets, La Radiotechnique, Philips, and Tesla show a heater for PCC88 of 7V. Another Philips data sheet shows 7.6V which is the one I have based the design on. Telefunken valves made by Siemens are quoted as 7V heater. I am bloody confused myself now. Thanks Alan but you say you use a Matsushita 7DJ8/PCC88 - That's exactly what I have here (and linked to previously at Watford Valves) yet you say it's not correct.... I am well confused.
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