Mystery Voltage Regulator? - Page 1
Forum section: electronics / projects

author: KRB
author_rank: Newbie
timestamp: June 08, 2024, 06:37:33 pm
content: To all:While trouble shooting a small circuit board I encountered what appears to be a voltage regulator (see attached picture). I googled the numbers on it was unable to come up with anything but voltage regulators for vehicle applications. Firstly, can anyone verify this is a voltage regulator? Secondly, can you direct me to a product data sheet for it?Many thanks.

author: Zero999
author_rank: Super Contributor
timestamp: June 08, 2024, 06:56:31 pm
content: I have no idea.The only way to know is to reverse engineer the surrounding circuitry, which is probably quite simple.

author: edpalmer42
author_rank: Super Contributor
timestamp: June 08, 2024, 07:03:09 pm
content: I can tell you that the brand is Teccor - I recognize the logo - but not much more than that. I don't think they did voltage regulators. They were big into transient suppressors and thyristors so it could be an SCR or Triac.

author: D Straney
author_rank: Frequent Contributor
timestamp: June 08, 2024, 08:17:06 pm
content: Was going to say the same thing as edpalmer; I saw alotof Teccor triacs with that logo when doing "competition analysis" teardowns of lamp dimmers.(Edit:) What device is this from? What's the rest of the circuit look like? It could be doing some kind of phase-cut regulation if it's connected to AC power.

author: KRB
author_rank: Newbie
timestamp: June 09, 2024, 01:52:02 am
content: Thank you for your replies. The circuit board is out of a Servo 140 power feeder for the X-axis on a milling machine. The feeder operates on 120VAC. Line 1 goes through an on-off switch which doubles as a 3amp circuit breaker. The feeder has left & right switch lever positions protected by limit switches. It has a potentiometer to adjust feed rate. Where things get interesting is speed is maintained at the adjusted lever no matter how deep a cut is made. If too large, the switch/breaker trips.The only schematic of the PCB is the one I’m attaching. It’s close to my circuit board but there are minor differences. The component in question is the “SCR-1, 54010L52TP”? Or something like that. It appears at the top of the pixelated picture. I’ve traced the associated components and they seem to be the same as mine.

author: Xena E
author_rank: Frequent Contributor
timestamp: June 09, 2024, 08:49:28 am
content: What schematic?..So it's definitely a thyristor.Perhaps just replace with a locally available one of generous ratings based on supply volts and you machines motor Power, (if it has failed).*Edit*Be wary though, that one may be an isolated tab type and it looks as if its riveted to the hardware, you could create a short if not careful...

author: Zero999
author_rank: Super Contributor
timestamp: June 09, 2024, 08:53:48 am
content: Quote from: KRB on June 09, 2024, 01:52:02 amFor future reference, please give all the background information in the first place. I might help people give better replies.QuoteSCR stands for silicon controlled rectifier, a type of thyristor.https://en.wikipedia.org/w/index.php?title=Silicon_controlled_rectifier&useskin=vectorAre you tying to repair/fault find? Why do you think it's the problem?

author: D Straney
author_rank: Frequent Contributor
timestamp: June 09, 2024, 02:12:50 pm
content: I can't see a schematic either, I'm guessing the attachment didn't work (don't remember if there was a "new member < X posts" limit on attachments). Sounds like it's running a DC motor, and it does speed control/regulates the DC voltage to the motor by firing the SCR a variable amount of time into the AC cycle:https://en.wikipedia.org/wiki/Phase-fired_controller

author: KRB
author_rank: Newbie
timestamp: June 09, 2024, 02:58:49 pm
content: My apologies, I thought I attached the schematic. Evidently my efforts didn’t work; I’ll try again. As I mentioned, it’s not very clear, it doesn’t exactly match my PCB, so my faith in it isn’t 100%. However, with the PCB in hand, I was able to verify all the components but the one I’m inquiring about.I intentionally kept my original post concise. Being a member of various other forums, I’ve found my interest wans when a member gives too much information.I’m a self-taught novice with electronics. I thought all components that looked like this were voltage regulators. When I couldn’t find it by the labels on it, I figured a senior electronics person would know right away what it is.Since I had the Servo 140 power feeder apart for cleaning and repair, I wanted to verify the PCB was okay. It’s a good opportunity to learn about a new (to me) component. Assuming it is an SCR, is it possible to verify it’s working correctly without power to the PCB?Trying to attach the schematic, I’m following the same steps as before. If it doesn’t show up, D Straney may be right. It may have something to do with my new member status.

author: Xena E
author_rank: Frequent Contributor
timestamp: June 09, 2024, 03:34:48 pm
content: Quote from: KRB on June 09, 2024, 02:58:49 pmIt's a simple phase angle trigger circuit. When coupled to a universal brushed motor, the back emf serves to control the trigger angle regulating the speed somewhat under varying load.The testing in circuit of the thyristor is limited to checking the gate/anode junction is good if you don't want to do it under power.If the thyristor is failed it will either not work, (open circuit), or overrun the motor, (dead short... allowing full AC)

author: KRB
author_rank: Newbie
timestamp: June 09, 2024, 05:27:06 pm
content: Xena E, thank you for the identification & description.The appearance of this SCR/thyristor gave me a weak belief it was a voltage regulator. This may seem like a silly question but I have to ask: besides voltage regulators, which circuit components are contained in housings that look like this SCR/thyristor? The obvious concern is how can I tell them apart without part numbers or schematics?

author: Xena E
author_rank: Frequent Contributor
timestamp: June 09, 2024, 05:46:12 pm
content: Quote from: KRB on June 09, 2024, 05:27:06 pmUnfortunately, almost anything with three leadouts that has a medium/high power capable encapsulation.When you become a little familiar with their construction you will be able to tell from the surrounding circuitry, and by doing some static testing of terminal resistances and inter terminal forward bias voltages.The short cut to all this is to buy a component analyser, they're avaliable for cheap, I have a Fnrsi one, just a few currency units to own, but they're not infallible.Get a copy of the book "Art of Electronics" old editions can be downloaded free, that will set you up with the basics of knowledge if you're keen to learnRegardsXena

author: Zero999
author_rank: Super Contributor
timestamp: June 09, 2024, 06:26:54 pm
content: Quote from: KRB on June 09, 2024, 05:27:06 pmUnfortunately that schematic is far too low resolution to see the full circuit. Please post a higher resolution if you can.That package, the TO-220 is used for a variety of power semiconductors: thyristors (TRIAC. SCR), transistors (BJT, MOSFET, IGBT etc.), voltage regulators (LM317, LM78xx, etc.) diodes (dual silicon/Schottky) etc. It can even be found with two leads for power resistor and single diodes.How do you know there aren't other components which have been damaged?

author: KRB
author_rank: Newbie
timestamp: June 09, 2024, 10:50:33 pm
content: Xena, I’ll look into the Art of Electronics. Thank you for the reference. I had never heard of the Fnirsi brand before. Looked around a little at them; impressive array of offerings. Do you mind telling me which model you have?Zero999, Unfortunately the schematic I posted is all I could come up with; clarity was my problem with it as well. I think there may be some proprietary considerations behind that but I’m not sure. Thank you for enlightening me on the TO-220 encapsulation style. I was unaware that shape/style had a designation. I was able to check all the resistors and diodes on the PCB. Turns out with the cables disconnected, it left one end of those components disconnected so I could measure their values straight off the board. There were two capacitors and two MOVs that I had to test out of circuit. All checked out ok so I had to leave the SCR untested. The unit is back together and running okay so it appears it was a good assumption. I wasn’t able to test it with the power on because of crowding and the cables that plug into the PCB are too short to pull it out where I could get at it. Not the best I suppose but it’s the best I could do with what I have and know. Each repair is a chance to learn more.

author: Xena E
author_rank: Frequent Contributor
timestamp: June 10, 2024, 06:31:52 am
content: Quote from: KRB on June 09, 2024, 10:50:33 pmYou're welcome.The unit we have for doing quick checks is the Fnrsi DSO TC3Cheap and cheerful.They are a bit of a toy but do include component ID, LCR function, and a functional but very basic low frequencysingle channel oscilloscope.It's handy if as I say you just want to make quick checks and don't need to fire up the grown up toys. We give them to the field service guys as they can just toss them into their toolbox, and it isn't the end of the world when they get trashed.I keep one on the office desk to do things like your posted question.Disclaimer:Other brands available, not a recommendation etc..I think they're around 40 gbp/$/€ in singles.Regards,Xena