Malfunction Of Both Relays Solved In V-GUARD Voltage Stabilizer V-G5
This Voltage Stabilizer was brought to me by an Electrician customer, with the complaint that relay was chattering. The female plug (output) was broken and just hanging on one screw. The plastic shield for the PCB, which would have been an insert between the PCB and core of the transformer, was found in pieces; probably due to heat and age!
After cleaning the inside and removing the PCB and relay from its holding screws, when I applied power, the power LED lit up, but I could not see any relay chattering. But the primary switching relay was stuck, and was found strained. So, after cleaning the PCB, replacing all electrolytic capacitors and retouching all the solder joints, and cleaning the board, I replaced this SPDT 12V, 250 Ohms 6A relay.
Then when I applied the power, the primary relay functioned after a few seconds delay and switched over to 3 minute timer relay. But that did not get on and I suspected the three vertically fit potentiometers, though I had sprayed it with WD40. We cannot clean it by turning it back and forth, as we might change the original timer and voltage settings. So, I removed all the three POTs, putting a mark 1, 2 and 3 and also marking its positions on the board. When I checked with my multimeter, two of the POTs were not having any contact from the center point. So I used a punch and gently tapped in the center for a proper hold of riveted portion. I also did the same on the other two ends. We need to be careful and gentle in doing these repair works, lest the POT should break. The idea was to measure the resistance from both sides and record it on a piece of paper for adjusting the new POTs.
Unless we set the new POTs exactly as the original, we cannot ensure factory setting of the timing and voltage cut off. Then replaced the three pots with horizontal type (all three POTs were 2.2K) pots that were only available with me and I bent the center pin to solder it on the board and extended the other two legs by cut pieces of components and fixed it firmly in place, making sure that the replaced POTs are in correct position on the board like the original.
Then when I applied power, the secondary relay did not function after a three minute delay, even though the voltage was available at the coils. The relay was in an open condition and I therefore just pushed the pole to the other position, upon which the output got on. So, the relay was indeed weak and needed replacement. As I was not having a DPDT 12V 250 Ohms 6A delay in stock, I fetched it from the market and replaced it. First I removed its outer cover just to watch whether the pole was engaging and fixed it and wired it. I had taken plenty of snaps of the wire connections in High Resolution mode to ensure reconnection in appropriate places. (Even the capacitors were not having any positive/negative markings on the board and I took enough pictures and put marks on the board underneath before replacing them.) Then when I applied power and measured the time from my digital watch, it got switched exactly at 2.53 Minutes, which was good enough.
Now, I had no Variac Transformer with me to check whether the voltage settings were ok and I assumed it should be as I had ensured same settings on the pot. All the five transistors, rectifier diodes, one Zener diode (6V) resistors were also checked by me thoroughly and I found them to be ok. I gave a load of 40W bulb and allowed it to be on for more than one hour and then replaced the female plug brought by the customer on my request. I soldered the relay wires properly before putting its cover and the final closing. You won’t find it so in the picture below, as it was taken just after doing a temporary connection. Mission accomplished with great satisfaction getting added to the collection.
This article was prepared for you by Parasuraman Subramanian from India. He is 74 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.
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Albert van Bemmelen
June 8, 2024 at 11:44 pm
These V-guard devices are still very uncommon in my country. We probably don't need those here at our stable AC 230 voltages.
And devices like our 3D printers these days have their very unique Power-Outage-protection build in its firmware to protect losing almost completely finished 3d printed objects, that took hours to print, after a sudden power loss. Because as soon as the Power is back on the 3D printer follows were it left off with the help of the on the internal SD card recorded object code that saved the exact gcode position until the moment the Power loss ocurred.
Something that also would be very helpful when burning Bluray or DVD discs that often also take long and would be wasted after a Power loss.
Parasuraman S
June 9, 2024 at 9:31 am
Many thanks for your expert comments and sharing your other experiences!
Imoudu.O
June 9, 2024 at 4:24 am
I'm yet to come across V.S having this kind of relay.Thanks for sharing sir.
Parasuraman S
June 9, 2024 at 9:32 am
Wish you get one soon! Many thanks!
Yogesh Panchal
June 9, 2024 at 10:36 pm
Good fix! Sir
Parasuraman S
June 10, 2024 at 9:32 pm
Thanks, Yogesh!
Hollis LuQuette
June 10, 2024 at 1:03 am
I had a power supply that gave me trouble diagnosing it .... There was a bad transistor that I replaced and still no go .... I checked everything that could go wrong , there was a zener diode that was in the circuit with the bad transistor . It checked good on 2 testers , I changed the zener and the power supply came back to life .... I saved the old diode and brought it to a friend that had a Curve tracer .... You guessed it , that zener was leaky , AKA breaking down under power , the little component tester and multimeter couldn't put a big enough load on it .... So it was time to build a homemade octopus that hooked to my O-scope to turn it into a curve tracer ...
Parasuraman S
June 10, 2024 at 9:33 pm
Thanks for your valuable share! Another thanks for your comments!
Waleed Rishmawi
June 10, 2024 at 6:51 pm
it is always a good idea to replace pots rather than cleaning them unless the pots are not avialable and I could understand that. I am glad it was back to life and as always, good job and keep up the good work. have a blessed day and thanks for sharing.
Parasuraman S
June 10, 2024 at 9:34 pm
Many thanks for your encouraging comments, dear friend!