Transformer rewind wire query

[Avo Mk8]

What is needed is the circuit diagram of the equipment. Have you explored obtaining that?
Or failing that, it would be worth you 'reverse engineering' the 400v circuit and drawing it out to see what you've got.
It does superficially look like the transformer is on the mains supply, so knowing how the 400v is obtained might help!

 

[Spike1947]

What is needed is the circuit diagram of the equipment. Have you explored obtaining that?

Yes that would of solved my quandary, have asked the makers, but all they give was the outputs etc that I posted, have asked again but up now no reply from them.

cheers
Spike

 

[Avo Mk8]

Yes that would of solved my quandary, have asked the makers, but all they give was the outputs etc that I posted, have asked again but up now no reply from them.

cheers
Spike

Nothing on the interweb? Is this a Megger PAT?

 

[Spike1947]

Nothing on the interweb? Is this a Megger PAT?

Robin SmartPAT 3000

 

[Spike1947]

Manual Robin SmartPAT 3000

 

[Lucien Nunes]

Well I'm only seeing one diode near the relevant secondary input terminals on the board, so it might even just be half wave rectified, does not look like a voltage doubler despite there being two electrolytics.

Do you know the history of this unit... is it definitely the original transformer? Could someone else have swapped it for an incorrect part? There's nothing special about Litz wire at 50Hz, the turns ratio is the turns ratio.

The splash on the board and vitreous resistors looks like a major arc has occurred, not just heat. Something like the adjacent 30A relay closing onto mains that shouldn't be there and spitting out metal. I presume it's the earth bond test relay.

 

[Avo Mk8]

Well I'm only seeing one diode near the relevant secondary input terminals on the board, so it might even just be half wave rectified, does not look like a voltage doubler despite there being two electrolytics.

Do you know the history of this unit... is it definitely the original transformer? Could someone else have swapped it for an incorrect part? There's nothing special about Litz wire at 50Hz, the turns ratio is the turns ratio.

The splash on the board and vitreous resistors looks like a major arc has occurred, not just heat. Something like the adjacent 30A relay closing onto mains that shouldn't be there and spitting out metal. I presume it's the earth bond test relay.

I wondered if the two electrolytics were in series (with resistors across) to get the voltage rating, as they look quite small!

I'm concerned at the idea of moving/re-soldering the resistors. If they've got really hot, the growth of intermetallic compounds in the solder has made the joints brittle and they will be difficult to work on, and the reliability will just get worse and worse with tinkering!
Am I worrying unnecessarily?
If it's arc splash rather than heat then maybe.

 

[Spike1947]

Well I'm only seeing one diode near the relevant secondary input terminals on the board, so it might even just be half wave rectified, does not look like a voltage doubler despite there being two electrolytics.

Do you know the history of this unit... is it definitely the original transformer? Could someone else have swapped it for an incorrect part? There's nothing special about Litz wire at 50Hz, the turns ratio is the turns ratio.

The splash on the board and vitreous resistors looks like a major arc has occurred, not just heat. Something like the adjacent 30A relay closing onto mains that shouldn't be there and spitting out metal. I presume it's the earth bond test relay.

Hi
Def it is only heat damage to the board, looks a lot worse than it is, relay is ok also, it just a very badley designed board, will alter the Ceramic resistors spacing etc, when I sort out the transformer winding, am sure that is the original transformer for this tester !.
Spike

 

[Avo Mk8]

Hi Spike

I see parallel activity on at least one other forum: allaboutcircuits, pretty well duplicating what's going on here, in the same timeframe!

Someone recently bought this model of tester on eBay for £8 (for spares).
I would keep an eye out for another! ?

 

[Spike1947]

Hi Spike

I see parallel activity on at least one other forum: allaboutcircuits, pretty well duplicating what's going on here, in the same timeframe!

Someone recently bought this model of tester on eBay for £8 (for spares).
I would keep an eye out for another! ?

Hi
Yes you are correct, is that condoned ?, I do keep looking on ebay, but would rather see if I can sort it myself though, bit of a challenge tbh.
Spike

 

[Spike1947]

I wondered if the two electrolytics were in series (with resistors across) to get the voltage rating, as they look quite small!

I'm concerned at the idea of moving/re-soldering the resistors. If they've got really hot, the growth of intermetallic compounds in the solder has made the joints brittle and they will be difficult to work on, and the reliability will just get worse and worse with tinkering!
Am I worrying unnecessarily?
If it's arc splash rather than heat then maybe.

 

[Spike1947]

Hi
I don't see a problem in raising the ceramic resistors away from the board and the relay, the new solder will replace what is there !.

I am wondering if, with the secondary winding that is laid on top of the primary , could it pick up any voltage from the primary !.

Spike

 

[Avo Mk8]

Hi
Yes you are correct, is that condoned ?, I do keep looking on ebay, but would rather see if I can sort it myself though, bit of a challenge tbh.
Spike

You obviously enjoy a challenge - but I was thinking another one for parts might be an overall cheaper and more reliable way of obtaining spares (eg a transformer!).

Do you know if the electronics still works?
If not, have you considered re-instating the transformer without the 425V winding, and seeing if the thing has survived? Or using a bench psu to run it? It would surely be frustrating to rewind the transformer only to find a trail of further issues?

 

[Avo Mk8]

Hi
I don't see a problem in raising the ceramic resistors away from the board and the relay, the new solder will replace what is there !.

You may find the solderability has become very poor, and difficult to get solder to flow to make a proper joint. It may not matter to you, but in the commercial world it's a concern, as the joints become unreliable.

I am wondering if, with the secondary winding that is laid on top of the primary , could it pick up any voltage from the primary !.

'pick up' only in the sense that insulation between the primary and secondary could break down. Thats why you need the layers of yellow polyester tape insulation between the two - as per your pics?

 

[Spike1947]

You obviously enjoy a challenge - but I was thinking another one for parts might be an overall cheaper and more reliable way of obtaining spares (eg a transformer!).

Do you know if the electronics still works?
If not, have you considered re-instating the transformer without the 425V winding, and seeing if the thing has survived? Or using a bench psu to run it? It would surely be frustrating to rewind the transformer only to find a trail of further issues?

No I don't, but that is exactly what I am going to do see post #18., then connect it up if I am getting a reading on the secondarys

Spike

 

[marconi]

If I employed someone to do some statutory periodic PAT testing for a fee and he/she turned up and used a PAT tester which they had repaired themselves after clear and major damage - I would refuse to pay them. And consider what else to do.......

But you may be doing this 'for fun' to see if you can get it working again and then you intend to bin it because the integrity of this test equipment is shot.

 

[Spike1947]

You obviously enjoy a challenge - but I was thinking another one for parts might be an overall cheaper and more reliable way of obtaining spares (eg a transformer!).

Do you know if the electronics still works?
If not, have you considered re-instating the transformer without the 425V winding, and seeing if the thing has survived? Or using a bench psu to run it? It would surely be frustrating to rewind the transformer only to find a trail of further issues?

No I don't, but that is exactly what I am going to do, see post #18, then connect it up if I am getting a reading on the secondarys

If I employed someone to do some statutory periodic PAT testing for a fee and he/she turned up and used a PAT tester which they had repaired themselves after clear and major damage - I would refuse to pay them. And consider what else to do.......

But you may be doing this 'for fun' to see if you can get it working again and then you intend to bin it because the integrity of this test equipment is shot.

Hi
Thanks for your reply, yes it is purely a challenge for me, and believe me I like a challenge , it also won't get into anyone elses hand, so def you won't be paying me to do any PAT Testing for you, actualy they don't use that term now, in the 18th edition it is called "Appliance Testing" , didn't include static Appliances but now does, so don't lose any sleep over it .

Spike

 

[Spike1947]

You may find the solderability has become very poor, and difficult to get solder to flow to make a proper joint. It may not matter to you, but in the commercial world it's a concern, as the joints become unreliable.

'pick up' only in the sense that insulation between the primary and secondary could break down. Thats why you need the layers of yellow polyester tape insulation between the two - as per your pics?

No, I meant any magnetic flux etc !.

 

[Lucien Nunes]

In an ideal transformer all the flux links all the windings. In practice the coupling is not perfect, hence leakage reactance. The physical arrangement thus affects the regulation and efficiency slightly, but not the the transformation ratio.

 

[marconi]

ps: The primary has roughly about 800 turns, 399 for the first layer !.
pps: Pic of PAT Tester board that the transformer feeds , it does a 500v DC test ! .

Spike