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Temp gauge problem required replacing the sending unit... Unless one wants to take all the covers off, you have to do it by feel. Make sure you get the correct sending unit... It has a larger thread than some. Have new ready to slam in as coolant will leak when you take old one out.

These are my changes to improve the Libby voltage regulator: Upon investigation, it appears that the original design was overdriving the gates of the SCR's. The following are changes I have made: 1. Replace the diodes CR16 and CR17 with 260 ohm, 1/4 watt resistors. This reduces the drive...

On consideration of the problem you have had, I think it might be that you are running the unit with voltage near the upper limit of its design. You might consider using some "control" transformers to permit operation at around the 416 design and say add another 24 or 48 volts to each phase...

There are two problems with the Libby regulators. One is they put diodes in the gate circuit of the SCR's. This allows the gates to float and be subject to transients and false triggering. The second problem is a long circuitous path on the circuit board for the output drive of the...

Be aware that I have discovered discrepancies in the technical manuals. One I just discovered is inconsistency in labeling of "Plugs" and "Jacks". Example is they are reversed for J5 and P5 from the schematics on my unit. I hope to make a video on rebuilding the Libby regulator and fixing the...

You will find that those fuses are expensive. You will have to replace the fuse before doing anything. Switching inductive loads like motors on and off may cause transients causing regulator to put out full current and blow the fuse. I have NOT traced out the regulator but it could have some...

I have the schematic for the Libby 50/60 Hz unit traced out. There is a design fault that is easily corrected and a board layout problem easily corrected with a jumper wire on the board.. I looked at photos of Libby 50/60 and 400 Hz and there are slight differences. The initial look on the...

I tested regulator on the generator today. This was with the generator unloaded. I could regulate the voltage between 200 and 250 as displayed on the meter. The voltage to the field appeared to be about 20 volts, however this is a pulsed drive from the SCR's and the Harbor Freight meter could...

Weather has precluded test for days... I have come up with one other modification I am installing. I am putting a "polyfuse" in the field lead. I am doing this by putting lugs on the polyfuse and connecting that to terminals 1 and 2. The wire that went to 1 is then put on terminal 2 which is...

Bench test shows same performance as the unmodified one in regards to the trigger pulses and regulation cutoff. The modification was easy. This should make the regulator far less sensitive to transients that could put it into run-away. I will still leave the 3 amp fuse in the field lead...

I am re-working the Libby regulator and have taken the series diodes out and replaced the gate drive resistors with 15 ohm resistors. Also have discovered another weak point. Due to the sloppy board layout, the path for the 39 ohm pull down for the Unijunction drive to the SCR's was a big...

I am surprised they didn't design the TRC to be a drop in replacement rather than requiring changing of the feedback scaling. I think these regulators were tinkered rather than engineered. In power equipment subject to electrical noise it is usually better to opt for lower impedance rather...

I don't have access to the TRC kit... so I will just correct the design defect in the Libby I have. Removing four parts and putting in two. A total of ten cents of parts. When I traced out the Libby circuit I could not believe they would make such a stupid mistake. It would cause the...

Yes, covered in conformal coating... use lots of heat and heat from the component side and suck from the circuit side. I had only minimal problem de-soldering. Used a regulated iron at 479 degrees. I had to carve out cancer where the MOV charred the board. The only possible thing the diodes...

I just bench tested the regulator and found that they do let the reference regulator go out of regulation during each half cycle by design. The main cause of failure I believe is letting the gates of the SCR's to float with a high impedance due to the series diodes in the gate feed. By...

The problem is poorly engineered gate drive to the SCR's that rectify the field voltage in a manner controlled by the regulating signal. Until I traced out the circuit I would not have seen the problem. I first have to design the gate drive resistors when I remove the series diodes to give the...

I had a one page reply set to send and just then our power failed... The gist of my reply was that the fuse added protected the field from being burnt up during failure of the regulator. I see two design defects in the regulator. One is lack of filtering on the rectified source powering the...

I traced out the circuitry of the Libby regulator. I may have found a design error. They rectify the power used to run the reference regulator and the unijunction pulser that pulses a pair of SCR's that generate the field current. This rectified supply is pre-regulated with what appears to be...