Motor control board repair

[cyclones]

Re: Motor control board

What type of motor does this have and what components are on the second board other than the ones on the heat sink

What redwire says -- a bunch of dual diodes and transistors.

[cyclones]

Re: Motor control board

Do both regulator ic's have a common ground?

I checked tonight in diode test mode between the AVR1 ground to the AVR2 ground and got a diode voltage drop -- about .595 volts.

[sam_sam_sam]

Re: Motor control board

What type of motor does this have and what components are on the second board other than the ones on the heat sink

[redwire]

Re: Motor control board

Either the -15V rail has wimped out and collapsed, or something is overloading the -15V regulator. It's not good for IC's and semi's power if a -ve rail goes +ve. I would put a reverse diode from each of the two rails to GND, to keep working on this.

The two VREG's look like on the main board two big heatsinks, the IC's are TOP-3 packaged, one says G/IN/OUT.
The second board has a bunch of dual diodes and transistors, I don't see a voltage regulator in the line up.

[eccerr0r]

Re: Motor control board

Odd both regulators are TO-3P and the board silkscreen says out-in(tab)-G which is typical for the negative rail regulator (should be in-G(tab)-out for positive). Make sure the "in" is the right voltage in any case.

These regulators are probably NOT for the motor but rather for the zillion op amps on the board that may control the motor drivers.

[R_J]

Re: Motor control board

It's nice top know one is getting warm, it would be nicer to know WHICH ONE? I will guess and say the +15 is getting warm and the -15 is not.
If both components have the same numbers it is unlikely they are both positive and negative voltage regulators

Do both regulator ic's have a common ground? have you checked the IN on the -15 ic to see if it has any voltage?
The transformer secondary is likely center tapped and the center tap goes to ground, and one part of the winding supplies each ~ on the bridge rectifier, then the + of the bridge supplies the positive IN for the +15v regulator and the - of the bridge supplies the negative IN of the -15 volt regulator

[cyclones]

Re: Motor control board

What are the numbers on the regulator ic's? especially the negative one. Doe the transformer only have 2 wires supplying the board or is it center taped?
you might want to indicate which one gets warm, is it the positive one or the negative one?
If you don't have a balanced circuit +15 and -15, you could see some positive voltage on the negative supply.

The two regulators which have heat sinks both have the following on them:
on the board they are labelled AVR1 and AVR2.

on the IC packages themselves, there is
3125p
6n27

on both. they seem to be identical, but only one is getting warm. The main transformer seems to have multiple taps.

[R_J]

Re: Motor control board

What are the numbers on the regulator ic's? especially the negative one. Doe the transformer only have 2 wires supplying the board or is it center taped?

There are two voltage regulators with large heat sinks on the board. One gets warm, and the other is room temp

you might want to indicate which one gets warm, is it the positive one or the negative one?
If you don't have a balanced circuit +15 and -15, you could see some positive voltage on the negative supply.

[cyclones]

Re: Motor control board

Here's a picture. There's a second board on the bottom that's almost entirely diodes and transistors. I checked all those with a meter and they seem good. I'll get a picture of the bottom board if needed.

[sam_sam_sam]

Re: Motor control board

Post a picture of this device so we can see how this is made so we might be able to figure out what might be going on

[cyclones]

I have a motor control board I am trying to repair. I've been told the motor is fine, but the control board will only make the motor go one direction but not the other. Power comes in through a linear transformer and then a rectifier bridge and then filter caps. No schematics for the board. Relays on the board are 24V so I started by setting my bench PSU to 24V and injecting voltage. There are several LEDs. All but one LED lights up. There are test points labelled +15V, 0V and -15V. When checking voltage potential between +15V and 0V, I get a perfect 15V. For -15V to 0V, my meter shows approximately +1.15V. There are two voltage regulators with large heat sinks on the board. One gets warm, and the other is room temp. I think i will check for input to the cold voltage regulator next, but I'm trying to figure out why I'm getting the +1.15V reading on the -15V.