Jump to content
CommodoreDecker

Troubleshooting hardware (Indus GT FDD and 1010 recorder)

Recommended Posts

Howdy!  So I've gotten an Indus GT disk drive from an auction. If nothing else I already know its belts are old and will be loose or will crumble. I'll be ordering belts shortly, but the unit also does not power on so there's a definite problem elsewhere. I whipped out the multimeter to test volts and amps.  The Indus PSU's label reads 11v/2a, and the multimeter shows volts wavering between 12 and 13, once reading an unpleasant 15.  The multimeter reads 0 amps output.  Assuming my meter isn't broken, the amps should read 2. I'm hoping I just have a bad PSU and not power board? (The Indus has 2 boards, one atop the mechanics that connects to a main board via ribbon cable, and the other where the power plug comes into it.  The board atop the mechanics has all-socketed chips...) This Indus has two honking huge voltage regulator modules and 4700mf capacitor (which is not bulging or leaking, the underlying circuit board looks in excellent condition) so it should be able to reduce that to 11v.  But if the PSU is wavering and inconsistent, it could have gone bad and could had possibly fried the Indus' power board (if nothing else). I'll try to finish taking it apart tonight, 

 

My 1010 recorder probably just needs belts as they're a little loose and springy to the touch, but I might as well ask as the mechanics otherwise seem to work -- but hitting rewind or ff shows a regular but slight jerky motion. Are there differences between worn belts and worn motor?  When attempting to load a program, the bzzzz____bzzzz____bzzz starts for a couple iterations before going into self-test mode (load failed).  One of the bzzzz noises was a little off-key, though going on memories some 33 years old, I recall a slight variance in tones... 

 

Thanks! 

 

 

Share this post


Link to post
Share on other sites

Indus GT uses 12vDC, unlike most other Atari drives that use 9vAC. (Including your 1010 - that takes 9V AC)

The brick inscriptions say 11.5vDC, but a bit over that is probably fine when unloaded.

 

Since the GT runs on DC, you'll probably have to work down the line on the PCB and check voltages seen at each step... According to the schematics, the 12V is used directly to power the drive motor, and two 7805 voltage regulators are used to make 2 +5v supplies. Check voltage seen at the in/out of each of those regulators

 

Schematics here:

https://atariwiki.org/wiki/Wiki.jsp?page=Indus GT Schematics

 

Specifically the power circuit:

gt-power.thumb.png.7e5cf8c733f1fd8b5569dde7ec31034a.png

Theres a number of small capacitors throughout that circuit that could also possibly need replacing... You might want to check for a short on the power input conenctor when the drive is switched "ON" - might be indicative of shorted capacitors...

 

I believe the Indus GT uses a Tandon TM-50 mech similar to the 1050, so you can buy new belt(s) from here:

https://console5.com/store/atari-1050-ibm-pcjr-qumetrak-142-floppy-drive-spindle-belt.html/

  • Like 1

Share this post


Link to post
Share on other sites
1 hour ago, CommodoreDecker said:

 The multimeter reads 0 amps output.  Assuming my meter isn't broken, the amps should read 2.

How did you try to measure that ?, also, the 2 Amps is the max output, the actual reading will be somewhat lower and depend

on what the drive is doing.

 

If you leave S2 open (i.e. OFF) then bridge the switch with the meter on pins 3 and 2, you should get a current reading.

  • Like 1

Share this post


Link to post
Share on other sites
8 hours ago, xrbrevin said:

 

Much thanks for that!!

 

They really did a nice job with content and layout.  The transformer did go above 13.0 in testing at one point, so I'm certain it's bad. I suspect the WART board might need to be replaced as well...  I'll try reseating the chips once I get the unit stripped down to that level. 

 

Assuming the PSU itself isn't wonky enough to fry the WART board, I wonder if the previous owner swapped DC and AC on the drive; the manual specifying not to do that because doing  so by accident would render the drive inoperable... a shame; if the Nintendo NES from a handful of years later could use AC or DC bricks so it was capable of converting an incompatible electricity type. then why not other hardware to foolproof it when they use standard off-the-shelf cylindrical connectors...  I'd bet real money that's what happened with the Indus.  

9 hours ago, TGB1718 said:

How did you try to measure that ?, also, the 2 Amps is the max output, the actual reading will be somewhat lower and depend

on what the drive is doing.

 

If you leave S2 open (i.e. OFF) then bridge the switch with the meter on pins 3 and 2, you should get a current reading.

 

Hmmm, I may have misread the label on the meter. (and how to read; the meter isn't going to be drawing much from the PSU now that I'm thinking about it...) 

 

Given that I did see the voltage crawl up to 15.x  then go down again, it is definitely  wonky.

 

10 hours ago, Nezgar said:

Indus GT uses 12vDC, unlike most other Atari drives that use 9vAC. (Including your 1010 - that takes 9V AC)

The brick inscriptions say 11.5vDC, but a bit over that is probably fine when unloaded.

 

Since the GT runs on DC, you'll probably have to work down the line on the PCB and check voltages seen at each step... According to the schematics, the 12V is used directly to power the drive motor, and two 7805 voltage regulators are used to make 2 +5v supplies. Check voltage seen at the in/out of each of those regulators

 

Schematics here:

https://atariwiki.org/wiki/Wiki.jsp?page=Indus GT Schematics

 

Specifically the power circuit:

gt-power.thumb.png.7e5cf8c733f1fd8b5569dde7ec31034a.png

Theres a number of small capacitors throughout that circuit that could also possibly need replacing... You might want to check for a short on the power input conenctor when the drive is switched "ON" - might be indicative of shorted capacitors...

 

I believe the Indus GT uses a Tandon TM-50 mech similar to the 1050, so you can buy new belt(s) from here:

https://console5.com/store/atari-1050-ibm-pcjr-qumetrak-142-floppy-drive-spindle-belt.html/

 

Much thanks! I'll do that tomorrow after I get out the WART board; the only way to test the capacitors is to remove them (I'll check for a short first, then start removing them to see which one(s) are bad... or I'll pick up an ESR circuit tester and get around desoldering...)  With luck it'd be that simple, just a short or bad capacitor... but I'll check the VRM outputs first to verify output voltage, one component at a time...

 

If the manual indicated not to use AC and the former owner had accidentally plugged in the wrong adapter, checking that might be a moot point but it's worth a try. (Or they were trying to get around the technical reasons.  But from what little I know and read, there'd surely be some form of scorching or visible somewhere... once I remove the drive section and the WART is fully visible any issues should be easier to spot.  AC into a DC device without any internal conversion would be bad news for sure...  that schematic shows a diode, but clearly AC can flow to any number of components and those would be fried, generally with visible signs of damage... maybe it is a short. AC would fry any of those capacitors, if nothing else deeper beyond that point. I'm just hoping the ICs themselves are okay, if nothing else...)  

 

Thanks for the explanation on the VRMs as well!

 

 

Share this post


Link to post
Share on other sites
6 hours ago, CommodoreDecker said:

the only way to test the capacitors is to remove them (I'll check for a short first, then start removing them to see which one(s) are bad...

given the cost of the capacitors, I would just replace them after the effort to remove them, I did complete cap

replacement on 2 1050 drives, even tho they were both working fine as it was so cheap to do, both drives still

working fine 35 years on :), caps replaced about 10 years ago

 

  • Like 1

Share this post


Link to post
Share on other sites

I finally got the unit disassembled. The sticker on the back holding in the board despite bending slightly the metal rear plate back, grr...   

 

Drive belt seems reasonably taut considering its age. Regardless, I should replace it. Like a rubber binder that's been out for decades and dried up, the belt will snap one day. 

 

The WART board looks pristine.

 

None of the chips were loose in their sockets... I might reseat them later, anyway.

 

ROM is v1.1. I'll order the newer version for this model if I can get this to power up.

 

Without powering up the unit but to check key areas, I couldn't find a short - so far, so good, I guess.  Ground was consistent to the VRMs (VREs?), as well as the voltage input. 

 

All of the capacitors look fine, no sign of bulging or anything - which doesn't mean they're not bad. I may as well replace those outright... my gut feeling is that the 4700uf one is toast. I should probably get an ESR meter too...

 

I'll power on and test voltages later, after today's coffee buzz wears off and re-reading the schematics so I don't fry anything, I'll try to get a reading from the VREs to confirm 5v and 12v output. I'll re-check the PSU first...

 

If nothing else and assuming the actual chips aren't damaged from (whatever caused the drive to not power up from the PSU), at least I've got spare parts of which most are likely useful.

 

 

Share this post


Link to post
Share on other sites
3 hours ago, CommodoreDecker said:

ROM is v1.1. I'll order the newer version for this model if I can get this to power up.

burn your own if you have an EPROM burner

  • Like 1

Share this post


Link to post
Share on other sites

One more update:  I re-checked the PSU: it hovered around  12.25V and  more consistenty. Not once after 2 minutes did it go above 13v.

 

I started checking the VREs. I should be expecting 5~7v, I get 0.85v on both of them.

 

Checking voltage at the  DC input itself on the board, it also reads 0.85v (which is not surprising).

 

Re-checking the PSU at the pliug after removing it from the board reads 12.2V. 

 

I'll try to check a cap after removing it from the board next. I'm not optimistic. With luck it won't read "0"...

 

Share this post


Link to post
Share on other sites

have you done a continuity test on the power caps in situ? i had a small electrolytic cap in a 1050 cause power on failure due to it becoming a dead short. C70 if i recall...

  • Like 2

Share this post


Link to post
Share on other sites
1 hour ago, CommodoreDecker said:

I re-checked the PSU: it hovered around  12.25V and  more consistenty. Not once after 2 minutes did it go above 13v.

You may not get a stable reading without a load, you could use a 12V automotive brake light bulb, the tolerance is 5% so voltage between +11.4 to 12.6VDC is good.

 

You may also want to take an AC voltage reading, I have an INGOT power supply with +5.4VDC, and 3.1VAC, on the DIN plug with a 6V flashlight bulb for a load. Without the load the DC output  is +5.95V.

When I built a power supply from scratch in the late 80's it wouldn't power up my 800XL, when I checked the output with an oscilloscope I found significant AC ripple on the +5VDC output, changing one of the capacitors fixed the problem. Luckily the AC ripple was enough to prevent the 800XL from working but not enough to do damage.

  • Like 2

Share this post


Link to post
Share on other sites
2 hours ago, xrbrevin said:

have you done a continuity test on the power caps in situ? i had a small electrolytic cap in a 1050 cause power on failure due to it becoming a dead short. C70 if i recall...

 

Not yet. I will be procuring a ESR tester shortly; I did some quick research and that's the only way to do it?  (Directly attaching the leads gave me the same 0.85v result as when testing the VREs...  either way, it looks like I'll need to get one.)

 

A short would prevent proper voltage being output at the VREs too... (I'm a bit green on this, think "Kermit the frog drunk on a cruise ship" sort of green...)  As I sit here, it really sounds like it'd be worth the time to replace the caps either way...

 

28 minutes ago, BillC said:

You may not get a stable reading without a load, you could use a 12V automotive brake light bulb, the tolerance is 5% so voltage between +11.4 to 12.6VDC is good.

 

You may also want to take an AC voltage reading, I have an INGOT power supply with +5.4VDC, and 3.1VAC, on the DIN plug with a 6V flashlight bulb for a load. Without the load the DC output  is +5.95V.

When I built a power supply from scratch in the late 80's it wouldn't power up my 800XL, when I checked the output with an oscilloscope I found significant AC ripple on the +5VDC output, changing one of the capacitors fixed the problem. Luckily the AC ripple was enough to prevent the 800XL from working but not enough to do damage.

 

Great idea about stable reading without load. Given some of the goofy readings I'd gotten, what you said fits the theory.  

 

Your mentioning capacitors as well - noting I have other equipment using the same uf rated capacitors, I should just order what I need along with the meter.  It's not going to hurt either way.  

 

Will order the caps (a shame Radio Shack isn't around any longer) and meter; fingers crossed that the caps are the sole problem. Sounds like it might be. 

Share this post


Link to post
Share on other sites

 

On 2/2/2021 at 2:51 PM, gilsaluki said:

Paul V. Alhart.  Lom Poc, CA.  The guy fixes all drives.  Fixed mine for very reasonable rate.

 

Thanks!  I will check him out if I run out of options... of which I'm down to one...

 

On 2/1/2021 at 9:32 AM, Nezgar said:

Indus GT uses 12vDC, unlike most other Atari drives that use 9vAC. (Including your 1010 - that takes 9V AC)

The brick inscriptions say 11.5vDC, but a bit over that is probably fine when unloaded.

 

Since the GT runs on DC, you'll probably have to work down the line on the PCB and check voltages seen at each step... According to the schematics, the 12V is used directly to power the drive motor, and two 7805 voltage regulators are used to make 2 +5v supplies. Check voltage seen at the in/out of each of those regulators

 

Schematics here:

https://atariwiki.org/wiki/Wiki.jsp?page=Indus GT Schematics

 

Specifically the power circuit:

gt-power.thumb.png.7e5cf8c733f1fd8b5569dde7ec31034a.png

Theres a number of small capacitors throughout that circuit that could also possibly need replacing... You might want to check for a short on the power input conenctor when the drive is switched "ON" - might be indicative of shorted capacitors...

 

I believe the Indus GT uses a Tandon TM-50 mech similar to the 1050, so you can buy new belt(s) from here:

https://console5.com/store/atari-1050-ibm-pcjr-qumetrak-142-floppy-drive-spindle-belt.html/

 

Rereading the manual, the voltages for the brick they discuss are all in line... (phew)

 

I did some further checking: The multimeter, in diode mode, shows 561 when I attach the leads. Swapping them, I get ~1100 that slows and stops at 1000. I'll retest later, I forgot to discharge the capacitors beforehand. But I also tested in resister mode, "1" is displayed regardless of which side I attach the wires. It's possible there's a shorted capacitor and I haven't yet removed said diode...

 

Using the manual's test involving hooking leads to J7 pins 1 and 2, I get 0 volts - the manual states that 0v here means it's a bad WART.

 

I took a close-up photo of the diode - when zooming in, it looks like it cracked right down the middle? It looks slightly askew too...  I'll remove it later this week and re-test it in isolation.

.20210209_091111.thumb.jpg.2fae3e274a3f3c689e9c552dcbc211f7.jpg

 

I'll find where R12 is and take a snapshot of that to see if it visibly looks damaged. Or better yet, test it for resistance.  

 

If nothing else, the diode is a definite culprit. If someone did swap power connectors with an AC unit, the caps could be toast as well. possibly R12, even if it looks pristine. The VRs both had readouts that didn't seem suspicious so that might be okay.  

 

I'll swap the diode first and then do followup multimeter readouts; with luck it's just the diode...

 

 

Share this post


Link to post
Share on other sites

also check power switch and barrel connector...

 

It wouldn't be the first time power was good right up until the jack on the board... damage by getting yanked side ways or broken joint... power switch internally stuck open from sitting for years etc...

check for 5 volts out of the voltage regulators in the indus... check for 11.x to 12.x in...

 

Edited by _The Doctor__

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...