Author Topic: Turbo Express with no 5v  (Read 210 times)

Dr Honda

  • Newbie
  • *
  • Posts: 15
Re: Turbo Express with no 5v
« Reply #15 on: September 23, 2020, 04:22:36 PM »
YES PLEASE !!  Thank you. Just check it in diode mode to see if there is a voltage drop between pins.  Or, any other method you can think of.  Oh... and could you tell me if there is any resistance between the tab on the B1182 and any of the 5v pins on the chips? (i'm getting around 4K)

As an FYI... since I can get the game to boot, and I get sound when I put 5v directly to the chip set (but not when I put it on the tab of the B1182)  I told the owner that the only way I may be able to save it is if I put a stand alone 5v regulator in it, and do a screen mod.  I know it sounds a little hack... but with this thing... there are just so many unknowns (like what Q503 is) that it may be the faster way to bring it to life.

Thanks again for the help

Keith Courage

  • Hero Member
  • *****
  • Posts: 2427
Re: Turbo Express with no 5v
« Reply #16 on: September 24, 2020, 01:41:03 AM »
Yes, you are correct that doing the Composite video mod+new screen would work. I've done this quite a few times for Express systems that have no image after a cap change.

Dr Honda

  • Newbie
  • *
  • Posts: 15
Re: Turbo Express with no 5v
« Reply #17 on: September 27, 2020, 08:20:49 AM »
.....
Afraid I have no idea what Q503 is or does. I have a stock GT here that I am about to work on, if you want me to test some points with a multimeter let me know and I will go over them when I have it cracked open.

Did you have time to check out Q503?  I've gotten most of the parts I need to convert the TE on my bench... but would still like to give it one more shot on getting it running in stock condition.

MasterofBiscuits

  • Newbie
  • *
  • Posts: 42
Re: Turbo Express with no 5v
« Reply #18 on: September 27, 2020, 03:01:57 PM »
.....
Afraid I have no idea what Q503 is or does. I have a stock GT here that I am about to work on, if you want me to test some points with a multimeter let me know and I will go over them when I have it cracked open.

Did you have time to check out Q503?  I've gotten most of the parts I need to convert the TE on my bench... but would still like to give it one more shot on getting it running in stock condition.

I did, only just this weekend. I didn't want to remove it so I tested in circuit, hopefully it's useful for comparison.

With anode on A and cathode on all other pins, it just gave me a fixed voltage with no drop.
With anode on B and cathode on other pins it gave me an open loop.

With anode on E I got a voltage drop on D and C but not on A or B.

Just seems to be a regular transistor.

I forgot to test the 5v line  ](*,) sorry.

Dr Honda

  • Newbie
  • *
  • Posts: 15
Re: Turbo Express with no 5v
« Reply #19 on: September 28, 2020, 09:23:20 PM »
Thanks for the info.  I will check that out tomorrow.

Dr Honda

  • Newbie
  • *
  • Posts: 15
Re: Turbo Express with no 5v
« Reply #20 on: September 29, 2020, 11:21:07 AM »
OK.... I'm getting the same thing.  Guess it's ok.  UGH.... LOL.

Well... I'm trying to get a few other things done... so I'll probably work on the mod toward the end of the week.  I'll post up with the outcome.  Thanks again for all the help.

MasterofBiscuits

  • Newbie
  • *
  • Posts: 42
Re: Turbo Express with no 5v
« Reply #21 on: September 30, 2020, 02:39:23 PM »
I just refurbbed a GT today that still had a very faint screen image even after all the caps had been replaced. I could see the game playing but barely - it seemed like the backlight was not at full power. I recapped it again and there was no change, so I replaced Q500, Q900 and Q901 and that fixed the problem. When I removed Q500 I got the fishy electrolyte smell, so I'm pretty sure that was the culprit. I was surprised about this as I'd cleaned the board twice with IPA and PCB cleaner . Keith has warned me about this previously and he was right!

In future I may remove this transistor and clean underneath as part of the recap process.

So if you haven't already, I would remove it and check (maybe replace it).

Dr Honda

  • Newbie
  • *
  • Posts: 15
Re: Turbo Express with no 5v
« Reply #22 on: October 05, 2020, 01:20:34 PM »
@masterofbiscuits

Thanks for the heads up on that.  Yes.  I did lift Q500, Q900 and Q901 off the board.  And you were right.  Q500 was "Fishy" when I removed it.   I checked it off line, and it seemed ok.  If this was my personal TE... I would just start replacing everything.  But it still doesn't answer why I don't have 5v... and why there is high resistance between the pad on B1182 and any of the "5v rail" connections.  I wish this would have been one of those times where a component would get hot so I could find it. But nothing is even warm with power on it.   I've checked all the caps again... I've checked the Zener... and I've checked a bunch of the transistors.

I talked with the owner last week, and he's ok with my idea of installing an external 5v regulator, and doing the LCD conversion.   At this point I think it's the fastest way to recovery.   And, ironically enough... I'm starting on it today.  I just built the consol5 video board, and stopped for lunch.  I'm going to head back down in a little while, and I'll put it on the main board, and see if I get anything.  I'll let you guys know what happens.
« Last Edit: October 05, 2020, 01:26:01 PM by Dr Honda »

MasterofBiscuits

  • Newbie
  • *
  • Posts: 42
Re: Turbo Express with no 5v
« Reply #23 on: October 05, 2020, 02:36:39 PM »
If you're doing a 5v mod, might as well put a lithium battery in there. I posted a guide on here not long ago, and I updated it the other day to make it a bit simpler. Doesn't require any case cutting, unless you want to add an LED and is fully reversible.

https://www.pcenginefans.com/forum/index.php?topic=23504.0

Definitely worth doing!



Dr Honda

  • Newbie
  • *
  • Posts: 15
Re: Turbo Express with no 5v
« Reply #24 on: October 06, 2020, 07:37:14 AM »
@masterofbiscuts

I saw your Lipo post when I was trying to find some answers on this TE.  I'm actually considering it with my own TE.  The only reason I haven't done anything like that yet is because mine is in good shape, and I would hate to cut it up.  If the prices weren't so crazy on these things... I would find a beater to convert.

OK... for an update... This TE is alive again !!   I spent so much time trying to figure out why I didn't have power... I almost feel silly now that I just didn't move forward with this conversion early on.  But then again... since this is someone else's money... I had to make sure.   But if I get another one like this... I will know, and I will just tell the owner that it's the only way to get it back.

So... I lifted Q500, B1182, the Zener off the board, and opened the bridge for the back light.  Then I added a 5v regulator.  It gets switched power from the input of where the B1182 was, and feeds the 5v rail directly at one of the memory chips.  I have it adjusted to 4.95v at 9.5v input (fresh batteries) and it will output 4.7v all the way down to 5v in. (Set with a bench power supply)   I then added the component board from Consol5.... and now she's working just fine.  I let it run for an hour on the bench, and nothing was even warm.  Today, I have a bunch of things I need to catch up on... but I'm hoping to mod the shell to fit the screen, and have it all buttoned up.

Thanks for all the help guys.

« Last Edit: October 07, 2020, 07:08:41 AM by Dr Honda »

Dr Honda

  • Newbie
  • *
  • Posts: 15
Re: Turbo Express with no 5v
« Reply #25 on: Today at 10:49:47 AM »
Hi All,

Thanks again for the help on this.

I'm not sure what the rules are... but the local used game store, who has me fixing stuff... talked me into video'ing some of the things that I find.   So, I documented this repair.  It turned into a 3 part video... but part 3 gives a good summery, and shows the screen mod. Here's the link if anyone is interested in what I did. I officially started the channel 2 weeks ago, and would love the support of the Turborafx crowd.  Oh... also ANY feedback would be appreciated.

https://youtu.be/-1d_ldl_fWs