Re: Paulmann electronic lighting transformer
Thanks Budm - and sorry for the typo; I meant on (not off) as you say!
I think that we agree - to turn on TR3 requires 0.6v which means greater than 3A peak through R7.
In the original circuit, this is never achievable, as the thermal fuse will have already failed, being rate at 2A max (although not the designed failure mode, this is 50% over rating).
I have verified the circuit, and it is correct - TR2 appears to be designed to stop the DIAC triggering, and not to sink the current once it...
stevenA
Member
Last Activity: 03-03-2014, 06:50 AM
Joined: 10-01-2012
Location: Paris
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Re: Paulmann electronic lighting transformer
Thanks to both of you for your input.
Budm, my analysis sugested that in principle, the voltage across R7 would be insufficient to turn off TR3. When TR3 is off, the Diac (32v DB3) will no longer fire TR2 at the start of the cycle and so it will shut down. Are you saying that as drawn (I believe it is correct, and corresponds to app notes that I have read), even if TR3 is switched on, the safety circuit will not work?
Ben 7, if I understand correctly you are suggesting that the thermal fuse blew because of increased...Last edited by stevenA; 11-01-2012, 04:57 PM.Leave a comment:
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Re: Paulmann electronic lighting transformer
After analysing this circuit, I have a number of questions!
1. It appears that the circuit failed because TR2 "shorted". TR2 and TR1 have similar loads except that TR2 is also the starter, initially switched on by the DIAC. In many similar circuits, a resistor of 10ohms is placed after the DIAC, pesumably to protect the transistor,although there is nothing in this one. How do you calculate the effect of the DIAC conducting on the base of TR2 (the max current through the DIAC and R9 would not appear to be enough...Leave a comment:
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Re: Paulmann electronic lighting transformer
Thanks for your replies.
In fact, a good part of the resistors were taken out when TR2 shorted and put 370v across most of the circuit (see the attached image with most of the bad ones removed)
I have matched with symmetry and through reading various application notes most of the resistor values, and am now checking them against the theory of a half bridge inverter - reading the values on some of these resistors is no game for the colour blind, and R4 is illisible!
Attached is my latest working...Leave a comment:
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Re: List of Bad Cap Manufacturers
Has anyone seen SHI capacitors - I know, someone actually chose to call their capacitors SHI(R) without the T.
Tried google but no joy....
I have a 10uF, 25v with 1.6ohm ESR and wanted to see the specs for a replacement (see Paulmann electronic transformer thread)Leave a comment:
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Paulmann electronic lighting transformer
Another day, another project!
This transformer (Paulmann 105H) failed ages ago, and I looked at repairing it today. It is a 230v AC 50Hz to 12v AC 40khz transformer for halogen lighting.
The actual fault was the microtherm thermal fuse glued to the top transistor in the attached photo.
I replaced this with a wire link to test and it then worked - for a few minutes! The thermal fuse was obviously doing its job. This was the only apparent fault.
The transistor is now out (short circuit) and it took a few resistors and another transistor... -
Re: Help needed with understanding this basic PSU design
Thanks Budm. I doubt that the meter I am using has true RMS, and do not (yet) have a scope.
If I understand correctly, you are saying that the output is via the TIC106D, and that the full bridge is only used to provide a voltage reference for the LM358 via the LM317, and a return path.Leave a comment:
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Re: Help needed with understanding this basic PSU design
Thanks Budm
I think that this is not in fact a PSU, but a battery charger! Following your above question, I have found similar circuits for a NiMh charger using similar components. That being said I would still like to understand how it works!
I do have the case but there are very few markings unfortunately - I cannot even remember what this supply was originally for but have an inkling that it could have been for a very early gen transportable phone
The markings are:
Approval...Leave a comment:
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Seuffer 1154 / Neff 195.190.388 Cooker Hood control
This control board is used in a variety of Siemens / Neff cooker hood products and eventually becomes intermittent - power cut offs, dead for varying periods etc as documented here [URL="http://www.elektronik-kompendium.de/forum/forum_entry.php id=156694&page=9&category=all&order=time"]http://www.elektronik-kompendium.de/forum/forum_entry.php id=156694&page=9&category=all&order=time[/URL] in German.
The principle suspect is the NPN transistor which is part of the supply, but the intermittance suggests that it may be related to supply voltage variations... -
Re: Help needed with understanding this basic PSU design
Thanks for your replies. This is only an exercise to help me improve my understanding of power circuits - this one is unusual (?) and I cannot see how it is working, particularly how the +ve output is linked to the -ve output, as the negative output is only connected via the supply to the LM358 to the rest of the circuit!
I have attached some photos as requested - and have overlaid components on the back of the PCB.
There were some errors in my previous circuit
, notably:
...Leave a comment:
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Help needed with understanding this basic PSU design
Good evening
I am trying to relearn some of the basic electronics that I have long forgotten, and would appreciate some help understanding how the attached reverse engineered circuit from a broken no-name PS is supposed to work!
This should supply 12v DC at 1.2 amp from 230VAC (the circuit may not be correct but I have checked it several times)
The supply does not work and I suspect the LM358 is at fault (the 370 ohm resistor to the inverted input is clearly overheating). The cap is bad.
I think (!) that this is a dual rail supply, and... -
Re: Suspect Bad PS Apple AcBel API 1PC36
After finishing the job and testing, I QC'd the components used and recorded actual results - as you will see in the attached, I actually used the wrong component for C35 - I had intended to use a UCC KY but had multiple caps and made the mistake. Hopefully should not be critical as this is a smoothing cap
...
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Re: Suspect Bad PS Apple AcBel API 1PC36
Thanks to all of your posts (especially Toasty and his lessons) I have just recapped a G4 MDD PS and solved the long running problem that it would only start with an ADC display connected.
For info, the bad caps were:
C16
C21
C29
C43
C60
C32
C45
and maybe C30 which was out of limits for my tester.
Said otherwise, all of the Teapo's removed had failed, and some of the L-Tec's. I suspect that the start up problem was linked to C32 or C45, although...Leave a comment:
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Re: D-Link router - faulty power brick?
Thanks to all on this forum I have started to hunt down bad caps in old failed equipment. My first try and first success this evening with the 220v powerbrick for a DGS1008D!
Very simple, just a transfo, bridge and 1000UF 16v Teapo cap that was actually about 600UF and 9ohm ESR! Gave the flashing lights error.
Replaced with Panasonic FM 25V - now works fine and the switch is in the reserve.
Next up is the Apple G4 MDD PSU!
Thanks again to all for your input and motivation, and to...Leave a comment:
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