Onoff Posted January 9, 2021 Share Posted January 9, 2021 Afternoon, Anyone help in identifying this PCB transformer make /spec? Other than it has a 220VAC primary originally. It's a bit cooked. I've Googled etc but drawn a blank. There's a label says 010921 420461. Then one side is screen printed: DT-4362-1 3323012 18/04/01 Cheers Link to comment Share on other sites More sharing options...
TonyT Posted January 9, 2021 Share Posted January 9, 2021 Are the windings intact and you can just measure the primary and secondaries? Link to comment Share on other sites More sharing options...
ProDave Posted January 9, 2021 Share Posted January 9, 2021 I would try powering it up to see if it is still intact and measure the secondary voltage that way. Can you post a pic of what it came from, presumably you have just de soldered it from a PCB? I take it the item was not working, are you sure it's the transformer, e,g a shorted bridge rectifier would stop it working and make the tx get all hot and bothered. Link to comment Share on other sites More sharing options...
Onoff Posted January 9, 2021 Author Share Posted January 9, 2021 2 hours ago, TonyT said: Are the windings intact and you can just measure the primary and secondaries? Intact? It's swollen and stinks to high heaven! Crispy is the word I'd use! ?Meters I have here measure up to 200MOhm. Open circuit on primary. This is all I get on the secondary: Voltage regulator us an LM317T. Going to start drawing it out. Link to comment Share on other sites More sharing options...
ProDave Posted January 9, 2021 Share Posted January 9, 2021 That test gear do you have access to? The LM371 is an adjustable voltage regulator. If it were me I would rig up any transformer I had to hand, fed from a variac. DC volt meter on the output of the LM371, crank up the input voltage on the variac until the DC output stabilised and did not rise any further, and them neasure the secondary voltage from my test transformer and order one to suit. the replacement might not be an exact drop in and may mean a bit of PCB buchery. But FIRST check those 4 diodes next to where the tx came out. If one or more is short that will be the reason it has cooked. What is it by the way? make and model number of the equipment? Link to comment Share on other sites More sharing options...
Onoff Posted January 9, 2021 Author Share Posted January 9, 2021 1 hour ago, ProDave said: That test gear do you have access to? The LM371 is an adjustable voltage regulator. If it were me I would rig up any transformer I had to hand, fed from a variac. DC volt meter on the output of the LM371, crank up the input voltage on the variac until the DC output stabilised and did not rise any further, and them neasure the secondary voltage from my test transformer and order one to suit. the replacement might not be an exact drop in and may mean a bit of PCB buchery. but FIRST check those 3 diodes next to where the tx came out. If one or more is short that will be the reason it has cooked. Ta. No Variac here. Just the assorted IR, Ohm and clamp meters, RCD & loop testers. Plus various "multi' and capacitance meters. Link to comment Share on other sites More sharing options...
ProDave Posted January 9, 2021 Share Posted January 9, 2021 Variable voltage DC power supply? Link to comment Share on other sites More sharing options...
Onoff Posted January 9, 2021 Author Share Posted January 9, 2021 @ProDave how can you edit and it not come up that you've edited? Mods privilege? ? It's a Carlo Gavazzi Dupeline FPD 1901 220 channel generator. Allows 8+ channel comms up 2 wires. Should be about 8vdc on the comms line. About 30 years old the tech. No big deal I can replace with an updated unit that's about 3 generations on from this. Carlo_Gavazzi-G34900000230-datasheet.pdf Link to comment Share on other sites More sharing options...
Onoff Posted January 9, 2021 Author Share Posted January 9, 2021 4 minutes ago, ProDave said: Variable voltage DC power supply? Mate's got it. Funnily enough the same lad who's trying to build a CNC table. (I gave him a CNC board @Jeremy Harris gave me as a weird aside). Link to comment Share on other sites More sharing options...
ProDave Posted January 9, 2021 Share Posted January 9, 2021 I have looked at the data sheet and none the wiser what it does. If you can borrow a DC power supply, connect that to the two transformer secondary terminals. Slowly wind the DC voltage up until the output voltage from the LM371 stops going up. that will then tell you the secondary voltage needed from the transformer, and measuring the DC current will tell you the rating. Link to comment Share on other sites More sharing options...
TonyT Posted January 10, 2021 Share Posted January 10, 2021 What is the unit you have? maybe an explanation of the device will help? Link to comment Share on other sites More sharing options...
Onoff Posted January 10, 2021 Author Share Posted January 10, 2021 3 minutes ago, TonyT said: What is the unit you have? maybe an explanation of the device will help? See a couple of posts back. Link to comment Share on other sites More sharing options...
TonyT Posted January 10, 2021 Share Posted January 10, 2021 Oops. A well what about a couple of 9v batteries in series, the IC can take 37 volts max so that should work Link to comment Share on other sites More sharing options...
Onoff Posted January 10, 2021 Author Share Posted January 10, 2021 (edited) The 4 diodes of the rectifier circuit check out OK. This then from the regulator datasheet: R1 in this case is 270R, R2 is 2400R. Not sure about IAdj so I just plumbed in 100uA as a figure. Vout then calcs as 12.6V.....I think? Edited January 10, 2021 by Onoff Link to comment Share on other sites More sharing options...
ProDave Posted January 10, 2021 Share Posted January 10, 2021 Okay so 12V out, I would try and find a 15V transformer. Buy the largest in terms of power that will fit the space. If you can find a pcb mount one with a matching pinout then happy days but unlikely and you might need to do some butchery. These are linear regulators and so they might be happy with a higher input voltage you don't want to go too high as it will just get hotter than whatever heatsink it has can cope with. Link to comment Share on other sites More sharing options...
Onoff Posted January 10, 2021 Author Share Posted January 10, 2021 40 minutes ago, ProDave said: Okay so 12V out, I would try and find a 15V transformer. Buy the largest in terms of power that will fit the space. If you can find a pcb mount one with a matching pinout then happy days but unlikely and you might need to do some butchery. These are linear regulators and so they might be happy with a higher input voltage you don't want to go too high as it will just get hotter than whatever heatsink it has can cope with. I've literally just ordered a 2VA 0-15V. A couple of mm taller. https://uk.rs-online.com/web/p/pcb-transformers/7320364/ Same 5mm pitch pins but the secondary pin out is different. I need to cut one track and bridge another. Should have the trannie on Tuesday. Link to comment Share on other sites More sharing options...
ProDave Posted January 10, 2021 Share Posted January 10, 2021 Looks good, probably as close as you are likely to find, Let us know how it goes. Link to comment Share on other sites More sharing options...
Temp Posted January 11, 2021 Share Posted January 11, 2021 Does the voltage rating of the Cin Capacitor help? Probably not as it could be way higher than needed. Link to comment Share on other sites More sharing options...
Onoff Posted January 11, 2021 Author Share Posted January 11, 2021 9 minutes ago, Temp said: Does the voltage rating of the Cin Capacitor help? Probably not as it could be way higher than needed. The 1000uF Cin is rated at 35V. Happy enough about Vout as dictated by R1/ R2. Link to comment Share on other sites More sharing options...
Onoff Posted January 12, 2021 Author Share Posted January 12, 2021 The 2VA trannie turned up. Though it'll fit on plan I reckon it'll be tight up against the case. Thinking a bit of airflow over the top is a good idea so I've ordered a 1.5VA. That'll give the nom. 3mm clearance like the original one had. Link to comment Share on other sites More sharing options...
ProDave Posted January 12, 2021 Share Posted January 12, 2021 Before ordering the smaller one, try it. This will at least confirm the voltage is okay. then leave it on 24 hours and see how hot it gets. You might not need an air gap if it runs cool. 1 Link to comment Share on other sites More sharing options...
Onoff Posted January 12, 2021 Author Share Posted January 12, 2021 36 minutes ago, ProDave said: Before ordering the smaller one, try it. This will at least confirm the voltage is okay. then leave it on 24 hours and see how hot it gets. You might not need an air gap if it runs cool. Smaller one's coming tomorrow. All of £3 I think it was. The only thing is when it's in its stainless steel enclosure on a roof, in the height of Summer it can get pretty hot in there. I've seen smd stuff literally dripping off of inverter boards. Link to comment Share on other sites More sharing options...
Onoff Posted January 14, 2021 Author Share Posted January 14, 2021 (edited) New 15VAC transformer fitted. Off load it measures nom 22VAC on the secondary. I've renewed the 4 diodes of the bridge rectifier, Cin the 1000uF cap and the voltage regulator. Applying power and measuring between Vout and ground and I'm seeing 4VDC. I calculated that should be just over 12VDC with the current values of R1 and R2. So what's pulling it all down I wonder... On the output of the unit itself I'm only seeing 1VDC...where I'm expecting around 8.2VDC. Pretty sure the output of this unit saw a prolonged short to ground which is what cooked the trannie in the first place. Edited January 14, 2021 by Onoff Link to comment Share on other sites More sharing options...
ProDave Posted January 14, 2021 Share Posted January 14, 2021 What is the ac voltage coming out of the transformer on load ? could it be overloaded? Raw ac Vout? Vdc direct from bridge rectifier? Link to comment Share on other sites More sharing options...
Onoff Posted January 14, 2021 Author Share Posted January 14, 2021 (edited) 1 hour ago, ProDave said: What is the ac voltage coming out of the transformer on load ? could it be overloaded? Raw ac Vout? Vdc direct from bridge rectifier? (22vac as aforementioned on the secondary, nothing connected, just applying 230vac on the bench). Transformer soldered in. Applying 230vac to A1 & A2, nothing connected to the output of the actual unit: 7vac across the secondary 5vdc direct from the bridge rectifier. Edited January 14, 2021 by Onoff Link to comment Share on other sites More sharing options...
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