Toshiba eStudio 2050 - dead except for 'main power light'

**nekowaiidesu** · 01-17-2017

Hi all,

I'm a bit stumped by this machine. The user reported that they turned it on but the control panel didn't show anything. When I got to the site it was a bit more severe.
When the machine boots only the 'main power' light on the control panel lights up. None of the keys work and on the computers the printer is shown as 'offline'.

Seemed like a power problem to me so I had a look at the main power supply board with nothing really to write home about. All the fuses are good and I don't see any damaged components. Next I had a look at the HVPS board. It was also covered in black toner and upon cleaning it up there was a single resistor with some blackness around it that wouldn't wipe off as easily as the toner did.

Now I have a few problems: I can't even really identify this resistor. the bands on it are: Green Blue Green Gold (?maybe silver.. difficult to tell?) Black
I'm not exactly an electrical engineer but one shouldnt need to be. Nevertheless I can't quite figure out what this resistor is. Why does it end with a black band? 0% tolerance?! My basic knowledge points me to 56.5 ohm (or maybe 5.65 ohm if it's silver instead of gold) but I suspect I am also reading these bands incorrectly...

Next I check it with the multimeter. I don't get a reading. but I don't suspect I would because my meter can only measure up to 2MOhm and I think this resistor (being on a HVPS) is actually much higher than 2 mohm (let alone 56.5)

So my next idea was, put the resistor and meter into a circuit with voltage and watch the amps. So I put 18V DC+ to the resistor, one terminal to the other side of the resistor, and the other terminal to the negative of the powersupply (should be a closed circuit with my meter and resistor and 18V) - I still get no reading. 0.00 micro amp.

I'm really not sure now if I am doing something wrong or if this HVPS is really the problem. Has anyone had similar problem? Only one LED is lighting up and the copier won't do anything. I've not found anything specific in the manuals about this. Any advice would be greatly appreciated, be it something else to test or maybe a way to test these resistors (heck, if someone can even correctly identify the resistor I would be a step further than I am now)

**blackcat4866** · 01-17-2017

Where to start ...

You've chosen a fairly arbitrary way of diagnosing your HVT. You would have as much luck smelling the boards for any components that smell burned.

I think if it was me, I would start by reading the outputs from the power supply and comparing them to the circuit diagram. When you first boot up, you only get 5vdc to the system board. Once the system board decides it's ready, it sends a signal to the power supply to provide the rest of the 5vdc, 24vdc, and whatever else you find on your circuit diagram. So if you're not getting the 5vdc to the system board initially, you have a failed power supply. If the 5vdc is present at the system board, but none of the other voltages are present, then I would look at the system board, or possibly something plugged into the system board.

Another thing that you can do is try to boot up into 3C or 08 mode to see if you can get in. You probably can't.

If you are convinced that you have some sort of a short in the HVT bringing down the voltages on the power supply, simply unplug all of the HVT connectors. If there is a dead short in the HVT the machine will boot up to an error message. Personally I think it's unlikely that your resistor has anything to do with the issue. =^..^=

**rapidocument** · 01-18-2017

Try to power it on with the doors opened, if theres something shorting it out you will get display on etc. until you close them,
also to spot a short I would disconnect ADF, finisher, etc.

Also I'd check power ON button and related wiring.

**nekowaiidesu** · 01-18-2017

Appreciate the patience and input @blackcat4866 and @rapidocument

These replies were very helpful. I should be able to get it working from here

P.S. and yeah, this became a big problem mostly because I left my meter at the office. Couldn't test much on site but the HVPS seemed (even smelled) suspect so I brought it back to the workshop not thinking that my meter is insufficient to read such high resistance. Confusion ensued, panic mode engaged, run to CTN and hope someone has some insight. Love you guys.

**crisblancio** · 01-18-2017

Originally Posted by nekowaiidesu

Appreciate the patience and input @blackcat4866 and @rapidocument

These replies were very helpful. I should be able to get it working from here

P.S. and yeah, this became a big problem mostly because I left my meter at the office. Couldn't test much on site but the HVPS seemed (even smelled) suspect so I brought it back to the workshop not thinking that my meter is insufficient to read such high resistance. Confusion ensued, panic mode engaged, run to CTN and hope someone has some insight. Love you guys.

i have the same problem on our toshiba 656se...tommorow i will check the power suplly unit....

BHALL · 09-30-2017

I have encountered a 2830 copier that had a similar issue. The main power light was on but the copier did not attempt to come to ready and the op panel was blank. This occurred after hurricane Irma. Eventually replaced the system board and problem solved. Read the manual before replacing. The little black box on the system board stays with the copier.

**sakisvas** · 10-01-2017

Check if the SYS board cooling fan is rotating... if yes update the firmware .

**prabhath731** · 03-11-2021

Originally Posted by blackcat4866

Where to start ...

You've chosen a fairly arbitrary way of diagnosing your HVT. You would have as much luck smelling the boards for any components that smell burned.

I think if it was me, I would start by reading the outputs from the power supply and comparing them to the circuit diagram. When you first boot up, you only get 5vdc to the system board. Once the system board decides it's ready, it sends a signal to the power supply to provide the rest of the 5vdc, 24vdc, and whatever else you find on your circuit diagram. So if you're not getting the 5vdc to the system board initially, you have a failed power supply. If the 5vdc is present at the system board, but none of the other voltages are present, then I would look at the system board, or possibly something plugged into the system board.

Another thing that you can do is try to boot up into 3C or 08 mode to see if you can get in. You probably can't.

If you are convinced that you have some sort of a short in the HVT bringing down the voltages on the power supply, simply unplug all of the HVT connectors. If there is a dead short in the HVT the machine will boot up to an error message. Personally I think it's unlikely that your resistor has anything to do with the issue. =^..^=

hey can you give me a circuit diagram?now i am big problem

**Phil B.** · 03-11-2021

Originally Posted by prabhath731

hey can you give me a circuit diagram?now i am big problem

it should be in the service manual..

your profile is scarce in info are you a certified tech?

**BillyCarpenter** · 03-11-2021

Originally Posted by nekowaiidesu

Appreciate the patience and input @blackcat4866 and @rapidocument

These replies were very helpful. I should be able to get it working from here

P.S. and yeah, this became a big problem mostly because I left my meter at the office. Couldn't test much on site but the HVPS seemed (even smelled) suspect so I brought it back to the workshop not thinking that my meter is insufficient to read such high resistance. Confusion ensued, panic mode engaged, run to CTN and hope someone has some insight. Love you guys.

Unless the resistor you're talking about is a "fusible" resistor, that's not what I'd be concentrating on. You're trying to do component level testing without testing the inputs and outputs. Also, it's not uncommon for a resistor to become discolored.