A.P.T valve stabilised PSU  

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Chris
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Joined:3 years  ago
Posts: 1657
16/11/2017 6:52 pm  
Posted by: PYE625

By the way, I seem to have lost some pictures from previous post's above, namely the circuit diagram I drew.

If you uploaded them, then they should appear in your uploaded files list. This allows members to reuse photos they have previously uploaded.  I've just looked through your uploaded files folder on the server and the photo's you mention are not there. This can mean one of two things, if its not in there, then it was not received or you've inadvertently deleted them which is possible as there is a delete button in the users attachments file manager tool.


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PYE625
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Posts: 1640
16/11/2017 7:07 pm  
Posted by: Chris
Posted by: PYE625

By the way, I seem to have lost some pictures from previous post's above, namely the circuit diagram I drew.

If you uploaded them, then they should appear in your uploaded files list. This allows members to reuse photos they have previously uploaded.  I've just looked through your uploaded files folder on the server and the photo's you mention are not there. This can mean one of two things, if its not in there, then it was not received or you've inadvertently deleted them which is possible as there is a delete button in the users attachments file manager tool.

Quite correct Chris, I did delete them as I thought they would all be repeated again along with the new pictures. I will be more careful in future to select the ones I want, and leave the other's.


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PYE625
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Posts: 1640
16/11/2017 7:10 pm  

Another mistake I somehow managed to make was with the AC voltage readings of the transformer secondary. I must have had the ground probe placed wrongly as I said there was 320-0-320 on the HT secondary. In fact, it is 375-0-375vrms and this explains why the unregulated HT is sitting just short of 500vdc. (This is of course relative to correct mains level input).


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Chris
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Joined:3 years  ago
Posts: 1657
16/11/2017 7:18 pm  

Posted by: PYE625

Quite correct Chris, I did delete them as I thought they would all be repeated again along with the new pictures. I will be more careful in future to select the ones I want, and leave the other's.

There's always one! 😆

Treat the forums attachments tool with the same respect you would your PC's file manager. If you delete a file you delete it from the system and hence your posts.

Guess this means I'll have to write another FAQ

By the way rather than taking your excellent thread off topic and cluttering it with this side-plot, you might have been raised the query in the help-desk section below. After all that's why I created it. This friendly advice and not criticism.

Edited: 6 days  ago

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PYE625
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16/11/2017 9:03 pm  

It's all new and I'm not used to it 🙁


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Katie_Bush
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Joined:3 years  ago
Posts: 854
16/11/2017 9:52 pm  
Posted by: PYE625

It's all new and I'm not used to it 🙁

In truth, I reckon it's all new to us all, rather like the first term in a new school? Then before we know it we'll all be finding our way around once more. thumb_gif


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Chris
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Joined:3 years  ago
Posts: 1657
16/11/2017 11:39 pm  

Agreed and if you think its hard from a user point of view, you want to try getting your head around all the admin server options/settings.  If I too was not finding my feet with all the new admin settings I would have ensured it was set so members could not delete their own files, ultimately I was to blame.

I remember the same disorientation was abound when we moved from PHPBB3 (Vrat) to the other forum (now old software) here. Anway, its now configured so it cannot happen again. As you say Marion, a few weeks from now we'll be working like pro's.

Edited: 6 days  ago

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PYE625
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19/11/2017 9:00 am  

Because there is no base cover to the PSU, it leaves components open to damage if knocked. So I made a base cover from an old steel speaker grille. I cut it to size and ground down the sharp edges then spray painted it with some Halfords grey primer. There are threaded inserts in the PSU base chassis, so it was a simple matter of finding some rubber feet, drilling the cover and screwing it in place.

Edited: 4 days  ago

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PYE625
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19/11/2017 10:14 am  

The 5k 2w wirewound pot that controls the set volts is very noisy and I have ordered a replacement from ebay. The replacement is the same spec and physical size, but is a 10-turn Spectrol pot so will give much finer control adjustment to the set volts output. 

Here is an example picture of the new pot....

Edited: 4 days  ago

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Cathovisor
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Posts: 1149
19/11/2017 11:55 am  
Posted by: PYE625

The 5k 2w wirewound pot that controls the set volts is very noisy and I have ordered a replacement from ebay. The replacement is the same spec and physical size, but is a 10-turn Spectrol pot so will give much finer control adjustment to the set volts output. 

Here is an example picture of the new pot....

Nice one. Spectrol pots are superb.


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Nuvistor
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19/11/2017 12:05 pm  

By the way the connectors and under chassis are not protected I am assuming it was designed to fit inside another cabinet.

Nice job again Andrew.

Frank


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PYE625
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19/11/2017 12:58 pm  
Posted by: Cathovisor

 

Nice one. Spectrol pots are superb.

They are indeed and I was able to find one for £11.  Sounds alot, but some were nearly £60 !!


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PYE625
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19/11/2017 1:02 pm  
Posted by: Nuvistor

By the way the connectors and under chassis are not protected I am assuming it was designed to fit inside another cabinet.

Nice job again Andrew.

Thanks Frank, yes I'm not sure as to the original design purpose, but it's ideal as a bench PSU for HT and LT needs. I have tested it on load and it is capable of providing at least 200mA at 300v, but as the fuse is rated at 250mA, I didn't attempt any higher demands.


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Cathovisor
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19/11/2017 5:38 pm  
Posted by: PYE625
Posted by: Cathovisor

 

Nice one. Spectrol pots are superb.

They are indeed and I was able to find one for £11.  Sounds alot, but some were nearly £60 !!

About the going rate - they were never cheap.


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PYE625
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19/11/2017 6:00 pm  

I have now re-drawn the circuit, here it is....

If anyone with better knowledge than me (shouldn't be too difficult, then) can describe how the circuit works, it will be interesting. The last diagram with the 85A2 (85v voltage reference) and the ECC81/3 are the interesting bits. It has to be said that I am assuming the valves are correct and in their correct positions. Swapping the ECC81 and ECC83 around makes little difference and it works just as well with two 81's or two 83's.

Edited: 4 days  ago

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PYE625
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19/11/2017 9:45 pm  

The approximate circuit voltages are as follows, with SET VOLTS at minimum (zero ohms), 215v regulated output.

ECC81 1st anode 215v , grid 134v, cathode 135.8v

ECC81 2nd anode 180v (control voltage to 3x EL86), grid 135v, cathode as above.

(85A2 is the 85v reference)

ECC83 1st anode 215v, grid 85v, cathode 85.6v

ECC83 2nd anode 134v, grid 85v, cathode as above.

 


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PYE625
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20/11/2017 9:59 pm  

I guess it had to happen eventually, yours truly manages to accidentally short the output and blow the fuse.

No problem, just fit another I hear you say. But this fuse is special. Typical. It is a 250mA Belling-Lee,  it is 15mm long and the end caps are slightly smaller than a standard 20mm type.

Of course, I don't have one, so I did the next best thing. I broke open a standard glass 250mA 32mm type and nicked the fine piece of fuse wire to replace the vaporised one in the small fuse. In the lower picture, you can see the end caps and they have the fuse wire soldered through tiny holes in the cap. Using a magnifier and tweezers, I was able to perform keyhole surgery and now have a good fuse !


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Katie_Bush
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Joined:3 years  ago
Posts: 854
20/11/2017 10:05 pm  

Been there and done that before, though not on anything special. Well done on taking the initiative and making a professional fix.


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PYE625
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20/11/2017 10:15 pm  

Thanks Marion, 

There happens to be some on ebay, but not exactly cheap. I may order one sometime though. I did think of changing the panel mounted fuse holder to a 20mm type, but the hole would need drilling out to a larger size plus it is too near the chassis edge to accept the new holder anyway. It is just in front of the GZ34 .......

Edited: 2 days  ago

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Katie_Bush
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Joined:3 years  ago
Posts: 854
20/11/2017 10:59 pm  

Hi Andrew,

I think it should be left alone, and then, how often do you plan to 'blow' a fuse? Given the relatively easy fix you just used, it's hardly worth all that extra work to modify the existing set up.

This reminds me of a Honda E300E generator we once had, and used a Honda specific fuse - that's where I did the repair job I mentioned above, but at 5A it was hardly special, just Honda wanting you to buy their fuses at about £3 each (at that time).

Marion


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Niall
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Joined:3 years  ago
Posts: 54
21/11/2017 2:19 pm  

Ack, those things! Just needs a fuse, pop it out, what the...

Rips it out and fits a standard 20mm holder, job done.

...time passes...

OK, just need a panel mount fuseholder to finish this, rake rake here's one. Get it fitted, grab a 20mm fuse, why wont it fit, oh right I remember now.

 


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Cathovisor
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Joined:3 years  ago
Posts: 1149
21/11/2017 2:40 pm  

Belling-Lee "OO" fuse, IIRC. About the same size as a BS 546 fuse, 5/8" long (or 15.9mm if you must.)

Might have some of those in the store...

Edited: 2 days  ago

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PYE625
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Posts: 1640
21/11/2017 5:09 pm  
Posted by: Cathovisor

Belling-Lee "OO" fuse, IIRC. About the same size as a BS 546 fuse, 5/8" long (or 15.9mm if you must.)

Might have some of those in the store...

Something at the back of my mind tells me this size of fuse was used in the wall outlet for electric clocks?


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Cathovisor
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Posts: 1149
21/11/2017 7:42 pm  

Posted By: PYE625

Something at the back of my mind tells me this size of fuse was used in the wall outlet for electric clocks?

The BS 546 fuse is indeed used in clock outlets. It was also used in some MK dimmer switches and it is also used in MK's fused BS 546 plugs.

Edited: 1 day  ago

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