5.84 and 6.62 either side of R2P, R3P, Pin4&5 of ecc83 and 5.84 on pins 4 & 5 of the ecc83, the pcc88's have 6.6v after the BB has been left to settle for a couple of minutes. This is with valves in.
I wonder if I should change the LED I put in place of ZD1P to get a higher output voltage rather than change the resistors?
I can actually see a very faint of glow from the heaters on all three valves, just two very faint points of light in each one if I have them somewhere gloomy, but I think you'd need to be in a darkened room to see them easily.
What have other people been using as ZD1P?
I wonder if I should change the LED I put in place of ZD1P to get a higher output voltage rather than change the resistors?
I can actually see a very faint of glow from the heaters on all three valves, just two very faint points of light in each one if I have them somewhere gloomy, but I think you'd need to be in a darkened room to see them easily.
What have other people been using as ZD1P?
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I follow the comments on my question. I am using the red LEDs as said in the bom - and they stay. I am not going to change anything because it is the best I have ever heard on my stereo.I haven't measured anything because I know that changing tubes change the amp again. I got a brand new record collection - all dressed nicely in 3D. Anything that could change is a new enclosure - sometimes in the future
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The Zener debate:
When Alan and I did the original BOM, we used a Phillips data's sheet to reference the correct heater voltage for the 2x PCC88
The data sheet clearly stated that the phillips PCC88 was 7.2v
However, we later discovered that almost every other PCC88 is 7v.
We changed the BOM to reflect this and the value fitted now is a 2v Zener.
I did post a link to the BOM on a thread here, which I thought was this one but I cant find it now, so I will repost a link later today.
If you use the MultiFET boards with the newer Jfets (yes they changed too due to becoming obsolete) then R11P will need changing from 330k to 390k, which lowers noise significantly.
We also built an extremely accurate inverse RIAA network and found a tiny overshoot in the HF end of the RIaa equalisation.
This was fixed by changing R10L&R from 68k to 71k.
You need to buy 1% 71.5k resistors and find the closest value, or make them out of two resistors in series.
Tried 0.1% 69.8k and they were close enough if you want an easy life [emoji6]
All of these little changes made improvements, so don't be afraid to adopt them.
When Alan and I did the original BOM, we used a Phillips data's sheet to reference the correct heater voltage for the 2x PCC88
The data sheet clearly stated that the phillips PCC88 was 7.2v
However, we later discovered that almost every other PCC88 is 7v.
We changed the BOM to reflect this and the value fitted now is a 2v Zener.
I did post a link to the BOM on a thread here, which I thought was this one but I cant find it now, so I will repost a link later today.
If you use the MultiFET boards with the newer Jfets (yes they changed too due to becoming obsolete) then R11P will need changing from 330k to 390k, which lowers noise significantly.
We also built an extremely accurate inverse RIAA network and found a tiny overshoot in the HF end of the RIaa equalisation.
This was fixed by changing R10L&R from 68k to 71k.
You need to buy 1% 71.5k resistors and find the closest value, or make them out of two resistors in series.
Tried 0.1% 69.8k and they were close enough if you want an easy life [emoji6]
All of these little changes made improvements, so don't be afraid to adopt them.
I'm using a BOM from ~October as that's when I ordered the components. I'm clearly behind the times 
Thanks for the info.
The reason for the Zener question was that I've killed two 1N4615 at ZD1P and it's a 2v .5w device. I put the first one down to heavy handed removal at the same time as replacing the VReg. But I was more careful with #2 and that was blown. So the voltage on the heaters was one thing, but I needed a Zener that can't be killed
Thanks for the info.The reason for the Zener question was that I've killed two 1N4615 at ZD1P and it's a 2v .5w device. I put the first one down to heavy handed removal at the same time as replacing the VReg. But I was more careful with #2 and that was blown. So the voltage on the heaters was one thing, but I needed a Zener that can't be killed
I use 2v 0.5w Zeners and have never blown one in over 40 builds. Sound like you may be having a different issue to me.I'm using a BOM from ~October as that's when I ordered the components. I'm clearly behind the times
The reason for the Zener question was that I've killed two 1N4615 at ZD1P and it's a 2v .5w device. I put the first one down to heavy handed removal at the same time as replacing the VReg. But I was more careful with #2 and that was blown. So the voltage on the heaters was one thing, but I needed a Zener that can't be killed
> and have never blown one in over 40 builds
I don't doubt it, I've seen photos of your builds and they're special. I'm not questioning or criticising BB or anything like that in any way.
In an age of punitive postage for small orders I wanted to optimise postage costs. I thought knowing which zeners other people have ordered would give me a chance... Just in case I was unlucky with the 2v zeners I chose.
I lack experience, I make mistakes, and I'm trying to be as methodical, cautious and careful as I can to minimise them. The only way I can learn is by looking at what other people have done, reading, doing, making my mistakes, then asking a lot of very dumb questions...
I don't doubt it, I've seen photos of your builds and they're special. I'm not questioning or criticising BB or anything like that in any way.
In an age of punitive postage for small orders I wanted to optimise postage costs. I thought knowing which zeners other people have ordered would give me a chance... Just in case I was unlucky with the 2v zeners I chose.
I lack experience, I make mistakes, and I'm trying to be as methodical, cautious and careful as I can to minimise them. The only way I can learn is by looking at what other people have done, reading, doing, making my mistakes, then asking a lot of very dumb questions...
I didn't think you were being critical [emoji4]
Just wondering if you have an issue elsewhere that's accumulated in the 2v Zener blowing.
I had lots of problems with the 7805, and I think the 2v zenner was blown by my constant changing and testing of the LT circuit. I've probably shorted something with a probe, and I would think that's what's maybe happened with you.
As for the zenner itself, the one that blew/was faulty on my board was from Farnell, the replacement which is working perfectly was from ebay, purely due to speed of delivery and no delivery cost. Here's a link.
BZX55C Zener Diode 2V to 30V 500mW 0.5W DO-35 Qty 10 - 20 - 50 - 100 pcs | eBay
What I'm trying to say is that I don't think there's an issue with different types or the quality of 2v zenners, but something else has caused the problem.
Something which does vary in quality are the 7805 regulators, you definitely need to be using the proper quality ones on the BOM, with the thick metal plate, as I found out to my cost.
As for the zenner itself, the one that blew/was faulty on my board was from Farnell, the replacement which is working perfectly was from ebay, purely due to speed of delivery and no delivery cost. Here's a link.
BZX55C Zener Diode 2V to 30V 500mW 0.5W DO-35 Qty 10 - 20 - 50 - 100 pcs | eBay
What I'm trying to say is that I don't think there's an issue with different types or the quality of 2v zenners, but something else has caused the problem.
Something which does vary in quality are the 7805 regulators, you definitely need to be using the proper quality ones on the BOM, with the thick metal plate, as I found out to my cost.
Those 7805 have been a nightmare for people.
I use a slightly different one now, but it's just because they are plentiful.
"Anything made by TI" is a safe bet.
I could easily have killed them both when I extracted them, I know they don't like mechanical stress.
Lacking a replacement Zener I used a reversed LED with a forward of 2.01v. I had a couple of 5v/2a vreg (old but reputable) in my spares box and with one of those I'm getting 9.4v at C1P and vreg input and 6.67v at VReg output with valves in. So still too low, probably 0.3-->0.5v?
I've ordered more Zeners (different), the Ti regulators and some green LEDs, so belt, braces and kitchen sink.
BTW, I got fed up binning resistors so I made Bin MasterTM
Lacking a replacement Zener I used a reversed LED with a forward of 2.01v. I had a couple of 5v/2a vreg (old but reputable) in my spares box and with one of those I'm getting 9.4v at C1P and vreg input and 6.67v at VReg output with valves in. So still too low, probably 0.3-->0.5v?
I've ordered more Zeners (different), the Ti regulators and some green LEDs, so belt, braces and kitchen sink.
BTW, I got fed up binning resistors so I made Bin MasterTM
Attachments
Just a point which confused me at the time. Along with a couple of multimeters and a lcr meter, I'm also using one of those cheapo Chinese component testers, as they're quick, easy to use and good for matching pairs, even if not accurate values.
When I've tested the correct high quality 7805's in it, it says they're faulty, yet when I've tested the thin plate rubbish version, it says they're ok. It was the fact it said the original 7805 was faulty that made me change it to a thin plate on from ebay (again for speed and lower cost) and started my adventure with 7805/2vzenner
The moral of the story being, if you're testing a 7805, use a multimeter.
When I've tested the correct high quality 7805's in it, it says they're faulty, yet when I've tested the thin plate rubbish version, it says they're ok. It was the fact it said the original 7805 was faulty that made me change it to a thin plate on from ebay (again for speed and lower cost) and started my adventure with 7805/2vzenner
The moral of the story being, if you're testing a 7805, use a multimeter.
Now I need your help.I got the Mazda tube today and I thought Id try it out.
But it must have gotten the wrong posision.When I started there where smoke and an explosion. R9P has gone up in smoke.
So there is no HV what is R9P for,and can the IRF820 have died to?
So I thought i would messaure the Filament....
And it turned out the PCC tubes got 9v and the ECC 7.1.
How do I lower that???
But it must have gotten the wrong posision.When I started there where smoke and an explosion. R9P has gone up in smoke.
So there is no HV what is R9P for,and can the IRF820 have died to?
So I thought i would messaure the Filament....
And it turned out the PCC tubes got 9v and the ECC 7.1.
How do I lower that???
Hi Ake
Sorry to hear that. As regards to the HV, i would suggest you ask Vivant, hopefully he's back from his holiday.
As for the high filament voltage, it sounds like the 7805 and 2v zener aren't doing their job.
As I understand it, the zener sits between the ground pin (centre pin) and ground, and boosts the voltage output of the 7805 by the value of the zener.
It sounds as if the 7805 has gone open circuit, and is letting the whole LT voltage through. which may have happened due to HT current being passed through it.
Try changing the 7805, and also the zener, as the 7805 may have blown it, and also you really need a 2v, not 2.7v.
Sorry to hear that. As regards to the HV, i would suggest you ask Vivant, hopefully he's back from his holiday.
As for the high filament voltage, it sounds like the 7805 and 2v zener aren't doing their job.
As I understand it, the zener sits between the ground pin (centre pin) and ground, and boosts the voltage output of the 7805 by the value of the zener.
It sounds as if the 7805 has gone open circuit, and is letting the whole LT voltage through. which may have happened due to HT current being passed through it.
Try changing the 7805, and also the zener, as the 7805 may have blown it, and also you really need a 2v, not 2.7v.