UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Computers

Notices

Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

Reply
 
Thread Tools
Old 1st Mar 2021, 12:03 pm   #721
ScottishColin
Heptode
 
Join Date: May 2012
Location: Perth, Scotland
Posts: 667
Default Re: Non-working Commodore PET 3016

OK - I've gone through UD6-UD9 pins 9, 10 and 11 (DA0-DA2) and got some varying results.

UD6
If I use Pin 20 on UD9, I get waves of c. 2V on pin 9, 4V pin 10 and 4V pin11.

However, if I use Pin 20 on UD7, the waves on UD9 definitely go up to c. 4V, 5V and 5V

UD7 and 8 are giving me consistent waves of 3v, 5V (spiking to 6) and 5v (spiking to 6) on pins 9, 10 and 11 respectively.

UD9 will only give me square waves if I use pin 20 on another IC (eg UD8) - the same voltages as UD7 and 8. However, if I use pin 20 on UD9, I get waves but they are very much not square ones like the others.

Would a document with some graphs be more helpful?

Colin.


Quote:
Originally Posted by SiriusHardware View Post
Resistances certainly look more uniform now although DA0 is a tad lower than the rest in both directiions.

What about DA0 and DA2 compared to the others on scope?
DA0 still half the size of the others?
DA2 still flatlined?
ScottishColin is online now   Reply With Quote
Old 1st Mar 2021, 12:20 pm   #722
ScottishColin
Heptode
 
Join Date: May 2012
Location: Perth, Scotland
Posts: 667
Default Re: Non-working Commodore PET 3016

Here's a document showing the difference in height of pins 9/10/11 UD9 against pin 20 UD9 or Pin 20 UD7.

https://drive.google.com/file/d/14l4...ew?usp=sharing

Colin.
ScottishColin is online now   Reply With Quote
Old 1st Mar 2021, 12:55 pm   #723
ScottishColin
Heptode
 
Join Date: May 2012
Location: Perth, Scotland
Posts: 667
Default Re: Non-working Commodore PET 3016

And as a final update this morning, I cannot get any waves from UD6 if I use pin 20 on UD6, only pin 20 from other PROMs.

Colin.
ScottishColin is online now   Reply With Quote
Old 1st Mar 2021, 4:03 pm   #724
Mark1960
Heptode
 
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 677
Default Re: Non-working Commodore PET 3016

DA0 is better when UD7 is enabled, but still driving to a lower voltage than the other data lines.

I don’t see the output on DA0 when UD8 or UD6 are enabled, but still suspect there is something loading the DA0 output of the proms and stopping them from driving as high as they should.

For the spikes on the data lines, I think this is just short time pulses with a 4MHz sample rate on 20us per division. You might want to check how they look at 10us or 5us per division, just to help your understanding of what you see on the scope, but I don’t have any concerns about those.

I think its time to consider removing the data bus buffer, maybe only the one connected to DA0. Unless anyone else thinks there is something else that could be stopping the proms driving DA0 to the same level as the other data lines.
Mark1960 is online now   Reply With Quote
Old 1st Mar 2021, 4:10 pm   #725
dave cox
Octode
 
dave cox's Avatar
 
Join Date: Jan 2009
Location: Bristol, UK.
Posts: 1,717
Default Re: Non-working Commodore PET 3016

I think you proved earlier that the CPU was running through the whole address range (activity on A0-A15) so the PROM UD6 *should* be selected (pin 20 low) at some point. I would be following the pcb trace/continuity from UD6/20 back to whatever drives it - it will some kind of address decoder, but i can't find a handy schematic to go further !

dc
dave cox is online now   Reply With Quote
Old 1st Mar 2021, 4:24 pm   #726
Mark1960
Heptode
 
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 677
Default Re: Non-working Commodore PET 3016

Sirius shows the address decoding in #683.

I think Colin was seeing the chip enable at UD6 but no data with chip enable low, but maybe Colin could confirm.
Mark1960 is online now   Reply With Quote
Old 1st Mar 2021, 4:52 pm   #727
ScottishColin
Heptode
 
Join Date: May 2012
Location: Perth, Scotland
Posts: 667
Default Re: Non-working Commodore PET 3016

All the PIn 20s seem to be driven from UD2 pins 14,15,16,17 (Sheet 1 of the schematics).

Should I see continuity from those pins to pins 20 on UD6/7/8/9 when the power is off - or do they only get continuity when something actually happens in UD2?

Colin.


Quote:
Originally Posted by dave cox View Post
I think you proved earlier that the CPU was running through the whole address range (activity on A0-A15) so the PROM UD6 *should* be selected (pin 20 low) at some point. I would be following the pcb trace/continuity from UD6/20 back to whatever drives it - it will some kind of address decoder, but i can't find a handy schematic to go further !

dc
ScottishColin is online now   Reply With Quote
Old 1st Mar 2021, 4:58 pm   #728
ScottishColin
Heptode
 
Join Date: May 2012
Location: Perth, Scotland
Posts: 667
Default Re: Non-working Commodore PET 3016

Here's what I see on Pin 11 (green) against either UD7 pin 20 (good) or UD6 pin 20 (bad).

https://drive.google.com/file/d/16nK...ew?usp=sharing

Colin.


Quote:
Originally Posted by Mark1960 View Post
Sirius shows the address decoding in #683.

I think Colin was seeing the chip enable at UD6 but no data with chip enable low, but maybe Colin could confirm.
ScottishColin is online now   Reply With Quote
Old 1st Mar 2021, 5:29 pm   #729
ScottishColin
Heptode
 
Join Date: May 2012
Location: Perth, Scotland
Posts: 667
Default Re: Non-working Commodore PET 3016

OK - I went back to UD2 pin 14 to see if that would trigger any data on the scope to UD6 Pin 11 - nothing, but it does with pin 15 (Sel D), so to me that points to a UD2 problem?

Colin.
ScottishColin is online now   Reply With Quote
Old 1st Mar 2021, 5:50 pm   #730
ScottishColin
Heptode
 
Join Date: May 2012
Location: Perth, Scotland
Posts: 667
Default Re: Non-working Commodore PET 3016

OK - just checked with power off - good continuity from pins 14, 15, 16 & 17 to UD6/20, UD7/20, UD8/20 & UD9/20 respectively.

Colin.

Quote:
Originally Posted by ScottishColin View Post
All the PIn 20s seem to be driven from UD2 pins 14,15,16,17 (Sheet 1 of the schematics).

Should I see continuity from those pins to pins 20 on UD6/7/8/9 when the power is off - or do they only get continuity when something actually happens in UD2?

Colin.


Quote:
Originally Posted by dave cox View Post
I think you proved earlier that the CPU was running through the whole address range (activity on A0-A15) so the PROM UD6 *should* be selected (pin 20 low) at some point. I would be following the pcb trace/continuity from UD6/20 back to whatever drives it - it will some kind of address decoder, but i can't find a handy schematic to go further !

dc
ScottishColin is online now   Reply With Quote
Old 1st Mar 2021, 6:13 pm   #731
Mark1960
Heptode
 
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 677
Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by ScottishColin View Post
OK - I went back to UD2 pin 14 to see if that would trigger any data on the scope to UD6 Pin 11 - nothing, but it does with pin 15 (Sel D), so to me that points to a UD2 problem?
No I think UD2 is ok, you see the chip selects on UD6, 7, 8 and 9 change from high to low, but you donít see any output on pin 11, DA2 from UD6 when UD6 chip select is low. I guess its possible that data in the first section of UD6 all has DA2 at 0, but it seems unlikely.
Mark1960 is online now   Reply With Quote
Old 1st Mar 2021, 6:19 pm   #732
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 7,338
Default Re: Non-working Commodore PET 3016

Doesn't seem to be anything wrong with UD2, which is producing the UD6 _CS1 (pin 20) pulse that you are showing on your yellow upper trace.

With power on, can you check the voltage on UD6 CS3 (pin 21)? (should be +5V).

When you are looking at UD6 pin 11 (D2) you are also looking at UD7 pin 7, UD8 pin 11, and UD9 pin 11 because all of those pins are connected together.

The fact that you have no activity on the D2 data line when UD6 _CS1 is low is surprising. As I recall, you just about got your Arduino Mega PROM reader working. If it's still lying around, try reading UD6 to see if it is still OK.
SiriusHardware is online now   Reply With Quote
Old 1st Mar 2021, 6:43 pm   #733
ScottishColin
Heptode
 
Join Date: May 2012
Location: Perth, Scotland
Posts: 667
Default Re: Non-working Commodore PET 3016

4.94V - same as UD7/8/9 pin 21.

I'll check the PROM.

Colin.

Quote:
Originally Posted by ScottishColin View Post
All the PIn 20s seem to be driven from UD2 pins 14,15,16,17 (Sheet 1 of the schematics).

Should I see continuity from those pins to pins 20 on UD6/7/8/9 when the power is off - or do they only get continuity when something actually happens in UD2?

Colin.


Quote:
Originally Posted by dave cox View Post
I think you proved earlier that the CPU was running through the whole address range (activity on A0-A15) so the PROM UD6 *should* be selected (pin 20 low) at some point. I would be following the pcb trace/continuity from UD6/20 back to whatever drives it - it will some kind of address decoder, but i can't find a handy schematic to go further !

dc
Quote:
Originally Posted by SiriusHardware View Post
Doesn't seem to be anything wrong with UD2, which is producing the UD6 _CS1 (pin 20) pulse that you are showing on your yellow upper trace.

With power on, can you check the voltage on UD6 CS3 (pin 21)? (should be +5V).

When you are looking at UD6 pin 11 (D2) you are also looking at UD7 pin 7, UD8 pin 11, and UD9 pin 11 because all of those pins are connected together.

The fact that you have no activity on the D2 data line when UD6 _CS1 is low is surprising. As I recall, you just about got your Arduino Mega PROM reader working. If it's still lying around, try reading UD6 to see if it is still OK.
ScottishColin is online now   Reply With Quote
Old 1st Mar 2021, 7:18 pm   #734
ScottishColin
Heptode
 
Join Date: May 2012
Location: Perth, Scotland
Posts: 667
Default Re: Non-working Commodore PET 3016

Good shout. It's blank - all 00s. Checked several times.

I checked UD7 with the same Arduino sketch and wiring and that reads ok.

Seems to me that I might need a new UD6....is this a fat-fingered possibility with the number of times I have been poking at it with a probe?

And can you point me at the right .bin so I can get a new UD6 from the same person as before?

Thanks.

Colin.


Quote:
Originally Posted by SiriusHardware View Post
Doesn't seem to be anything wrong with UD2, which is producing the UD6 _CS1 (pin 20) pulse that you are showing on your yellow upper trace.

With power on, can you check the voltage on UD6 CS3 (pin 21)? (should be +5V).

When you are looking at UD6 pin 11 (D2) you are also looking at UD7 pin 7, UD8 pin 11, and UD9 pin 11 because all of those pins are connected together.

The fact that you have no activity on the D2 data line when UD6 _CS1 is low is surprising. As I recall, you just about got your Arduino Mega PROM reader working. If it's still lying around, try reading UD6 to see if it is still OK.
ScottishColin is online now   Reply With Quote
Old 1st Mar 2021, 7:49 pm   #735
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 7,338
Default Re: Non-working Commodore PET 3016

If it is duff, that's a shame - it was definitely OK when I had it (correct checksum, etc) but they are notoriously fragile. That's the one where the pin had broken off on the corner, isn't it, so maybe it's better in the long run to replace it anyway.

The file you would be looking for for UD6 is the one named thusly:-

basic-2-c000.901465-01.bin2009-08-18

under 'Files' on this page:-

http://www.zimmers.net/anonftp/pub/c...pet/index.html

UD7 which you've already replaced should have been programmed with the file named:-

basic-2-d000.901465-02.bin2009-08-18

If you are wondering how I know which code goes where, look closely at the circuit diagram of the PROMs, which shows the address range occupied by each PROM. UD6 = C000 onwards, UD7 = D000 onwards. Those two hexadecimal addresses are included as part of the file names above.
Attached Thumbnails
Click image for larger version

Name:	2001N_PROMS_sch.jpg
Views:	18
Size:	72.1 KB
ID:	228017  

Last edited by SiriusHardware; 1st Mar 2021 at 7:58 pm.
SiriusHardware is online now   Reply With Quote
Old 1st Mar 2021, 8:42 pm   #736
julie_m
Dekatron
 
Join Date: May 2008
Location: Derby, UK.
Posts: 7,732
Default Re: Non-working Commodore PET 3016

The schematics for this PET model can be found here.

If you can't find the exact PROM at a reasonable price, it should be easy enough to bodge in the more readily available 2764. This even has enough room to do double duty as both UD6 and UD7.
__________________
If I have seen further than others, it is because I was standing on a pile of failed experiments.
julie_m is offline   Reply With Quote
Old 1st Mar 2021, 8:51 pm   #737
ScottishColin
Heptode
 
Join Date: May 2012
Location: Perth, Scotland
Posts: 667
Default Re: Non-working Commodore PET 3016

Thanks - I've found someone who supply and burn for a tenner so I'm happy with that. I'd love to know what I did.

I plan to get some new 24 pin sockets and put the PROMs into sockets so that if I need to remove them, I will remove the socket with the PROM in it, not just the PROM.

Hopefully that might save the legs a little if nothing else.

Colin.


Quote:
Originally Posted by julie_m View Post
The schematics for this PET model can be found here.

If you can't find the exact PROM at a reasonable price, it should be easy enough to bodge in the more readily available 2764. This even has enough room to do double duty as both UD6 and UD7.
ScottishColin is online now   Reply With Quote
Old 1st Mar 2021, 9:09 pm   #738
ajgriff
Octode
 
ajgriff's Avatar
 
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 1,962
Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by ScottishColin View Post
I'd love to know what I did.
You probably didn't do anything. One thing I have learnt about early PETS is that chips can and do give up the ghost without the slightest provocation!

Alan
ajgriff is online now   Reply With Quote
Old 2nd Mar 2021, 1:53 am   #739
Mark1960
Heptode
 
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 677
Default Re: Non-working Commodore PET 3016

Which of the proms was already replaced?

Does it show a better high voltage level than the others on DA0 ?

I think you still need to try and identify why DA0 is not showing a good high level. If it turns out to be the buffer its possible this could have caused the failure of UD6.
Mark1960 is online now   Reply With Quote
Old 2nd Mar 2021, 10:54 am   #740
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 7,338
Default Re: Non-working Commodore PET 3016

UD7 is the one which was recently replaced. When I had them briefly that was the only one of the four which was dud. I didn't get the character PROM UF10, but Colin read that with an Arduino shortly afterwards and it looked OK.

Shall we ask Colin to replace the data bus buffers if he is going to be waiting for a replacement UD6 anyway?
SiriusHardware is online now   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 4:55 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.