16 Aug
2009
16 Aug
'09
5:06 p.m.
Hey.
I picked up a freebie CBM/PET 8032 system with dual disk drive and Z80 board
a few weeks ago. It didn't power up. I put it on my workbench and opened
"the hood" to suddenly find out that the CRT was not secure, because it hit
my workbench neck first, and broke the clear glass at the end of the tube. I
was wondering if it is possible to find a replacement tube. Could I somehow
(on a really long shot) get a same sized CRT from a black&white TV to fit
inside and work?
Any advice or suggestions very appreciated.
Thanks
Joe Giliberti
17 Aug
17 Aug
5:56 a.m.
was wondering if it is possible to find a replacement
tube. Could I
somehow
(on a really long shot) get a same sized CRT from a black&white TV to fit
inside and work?
**any** tube that fits in place will work. Believe me. You can use one
from a B&W tv or a green phospor (or ambar, or
whatever) computer monitor.
6:41 a.m.
Awesome. I thought it was a long shot, but I had heard of something similar
having been done before. I got it from a guy in Pennsylvania, who also
donated a Cromemco Z2-H and some homebrew stuff toward the MARCH museum.
As far as my PET, the only sign of life I can see is the illumination of an
LED on the board. In the interests of troubleshooting, I have removed the
z80 board and put the 6502 back in its socket. Does anyone have a PDF of
some type of service manual? It could be helpful.
Thanks everyone!
Joe Giliberti
On Mon, Aug 17, 2009 at 8:56 AM, Alexandre Souza <
alexandre-listas at e-secure.com.br> wrote:
was wondering if it is possible to find a replacement
tube. Could I somehow
(on a really long shot) get a same sized CRT from
a black&white TV to fit
inside and work?
**any** tube that fits in place will work. Believe me. You can use one
from a B&W tv or a green phospor (or ambar, or whatever) computer monitor.
7:53 a.m.
As far as my PET, the only sign of life I can see is
the illumination of
an
LED on the board. In the interests of troubleshooting, I have removed the
z80 board and put the 6502 back in its socket. Does anyone have a PDF of
some type of service manual? It could be helpful.
I'm pretty sure google is your friend :) And with the service manual,
maybe you can get the composite video line that goes to the monitor and show
it up on a tv or external composite monitor :o)
8:04 a.m.
On Mon, Aug 17, 2009 at 10:53 AM, Alexandre
Souza<alexandre-listas at e-secure.com.br> wrote:
There are a couple of simple (1-chip) circuits to do that and I've
built one of them. I could get legible text on a "standard" B&W
security monitor, but I never did get the horizontal hold to be
stable.
It was good enough to prove the machine was running (I did see the
usual ROM splash message in the corner), but it wasn't possible to use
the machine in that state.
Perhaps you might have better luck, but that was my experience with an
external composite monitor adapter circuit a year ago.
-ethan
As far as my
PET, the only sign of life I can see is the illumination of
an
LED on the board. In the interests of troubleshooting, I have removed the
z80 board and put the 6502 back in its socket. Does anyone have a PDF of
some type of service manual? It could be helpful.
? I'm pretty sure google is your friend :) And with the service manual,
maybe you can get the composite video line that goes to the monitor and show
it up on a tv or external composite monitor :o)
8:21 a.m.
There are a couple of simple (1-chip) circuits to do that and I've
built one of them. I could get legible text on a "standard" B&W
security monitor, but I never did get the horizontal hold to be
stable.
It was good enough to prove the machine was running (I did see the
usual ROM splash message in the corner), but it wasn't possible to use
the machine in that state.
Perhaps you might have better luck, but that was my experience with an
external composite monitor adapter circuit a year ago.
--------------------------------------------------------------------------------
I'm too busy to download the schematic and take a look right now, but
I'm pretty sure the horizontal hold was due to the need of an external
inversor in the horizontal sync pulse.
8:05 a.m.
Alexandre Souza wrote:
Some CRT's can be found here:
http://www.magnetosphere.net/
was wondering
if it is possible to find a replacement tube. Could I
somehow
(on a really long shot) get a same sized CRT from a black&white TV to fit
inside and work?
**any** tube that fits in place will work. Believe me. You can use
one from a B&W tv or a green phospor (or ambar, or whatever) computer
monitor. 
11:28 a.m.
Hey.
I picked up a freebie CBM/PET 8032 system with dual disk drive and Z80 board
a few weeks ago. It didn't power up. I put it on my workbench and opened
"the hood" to suddenly find out that the CRT was not secure, because it hit
my workbench neck first, and broke the clear glass at the end of the tube. I
was wondering if it is possible to find a replacement tube. Could I somehow
(on a really long shot) get a same sized CRT from a black&white TV to fit
inside and work?
Almost certainly yse. Monochrome CRTs are pretty generic.
You need to find one with the same diameter neck (there are basically 2
sizes) and same pin base (this, I think, is 'modified B7G' with 7 pins).
Get that right, and you'll have a CRT that is pretty much going to be
electircally similar.
Keep the PET's deflection yoke (don't try to use the one from the TV).
-tony
12:14 p.m.
When I get home, I'll see what I can do
Basically, the following have to match between the old and new CRTs
Deflection angle (almost certainly 90 degrees)
Neck diameter
Pin base
Heater voltage.
My experience is that small monochrome CRTs come in 2 classes. Those with
a thin neck, modified B7G base (like a 7-pin miniature valve, but with
the seal-off tube in the middle) and 12V heater. And those with a thicker
neck, B8H base (8 pins in a circle with a plastic keyway thing in the
middle around the seal-off tube) and a 6.3V heater.
The former is more common in classic computers and also in portable TVs.
I have seen a few of the latter in computers, though.
So if you get the right base and thus neck diameter, the yoke will fit,
the base connector will fit, and the heater voltage will be right.
The other electrode voltages (BTW, the pinout seems to be pretty much
standardised within a classs) are much less critical. You'll get
_something_ on the screen, you may have to tweak things a little to get
it perfect.
-tony
6:43 p.m.
I extracted the tubes from the TV and PET. The yoke and connectors fit. I
have not yet powered it yet. Step by step...
On Mon, Aug 17, 2009 at 3:14 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
When I get home, I'll see what I can do
Basically, the following have to match between the old and new CRTs
Deflection angle (almost certainly 90 degrees)
Neck diameter
Pin base
Heater voltage.
My experience is that small monochrome CRTs come in 2 classes. Those with
a thin neck, modified B7G base (like a 7-pin miniature valve, but with
the seal-off tube in the middle) and 12V heater. And those with a thicker
neck, B8H base (8 pins in a circle with a plastic keyway thing in the
middle around the seal-off tube) and a 6.3V heater.
The former is more common in classic computers and also in portable TVs.
I have seen a few of the latter in computers, though.
So if you get the right base and thus neck diameter, the yoke will fit,
the base connector will fit, and the heater voltage will be right.
The other electrode voltages (BTW, the pinout seems to be pretty much
standardised within a classs) are much less critical. You'll get
_something_ on the screen, you may have to tweak things a little to get
it perfect.
-tony
18 Aug
18 Aug
7:03 a.m.
haha.
Its all back together. It still doesn't work. When I switch it on, all I can
hear/feel is 60Hz in the area of the transformer.
On Mon, Aug 17, 2009 at 10:08 PM, Ben <bfranchuk at jetnet.ab.ca> wrote:
Joe Giliberti wrote:
I extracted the tubes from the TV and PET. The
yoke and connectors fit. I
have not yet powered it yet. Step by step...
From the other room ... *Put back the TV , my soap's on NOW!*
12:53 p.m.
haha.
Its all back together. It still doesn't work. When I switch it on, all I can
hear/feel is 60Hz in the area of the transformer.
I'd forget the CRT/monitor section for the moment, and try to get the
digital side working.
What test gear do you have?
I think you can fairly easily find schematics for the 8032. Start by
checking the power rail(s?) -- particularly that uyou have 5V to all the
logic chips. Make sure the master clock is running. Make sure the CPU is
doing something. Does it initialise the 6845 -- check the Vsync and Hsync
outputs of that chip to see if they are running at sane frequencies.
That should get you started...
-tony
1:33 p.m.
I have a good DMM available, as well as a scope.
I just noticed that there are two chips missing, which appear to be ROMs.
There are sockets, but no chips. Their location would be toward the back
part of the board, to the right. They are the last two in a column (in
relation to the back) of similar-sized chips, most of which are direct
soldered to the board. I can take a photo if one is needed
On Tue, Aug 18, 2009 at 3:53 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
haha.
Its all back together. It still doesn't work. When I switch it on, all I
can
hear/feel is 60Hz in the area of the transformer.
I'd forget the CRT/monitor section for the moment, and try to get the
digital side working.
What test gear do you have?
I think you can fairly easily find schematics for the 8032. Start by
checking the power rail(s?) -- particularly that uyou have 5V to all the
logic chips. Make sure the master clock is running. Make sure the CPU is
doing something. Does it initialise the 6845 -- check the Vsync and Hsync
outputs of that chip to see if they are running at sane frequencies.
That should get you started...
-tony
1:41 p.m.
On Tue, Aug 18, 2009 at 4:33 PM, Joe Giliberti<starbase89 at gmail.com> wrote:
I have a good DMM available, as well as a scope.
Good start.
I just noticed that there are two chips missing, which
appear to be ROMs.
There are sockets, but no chips. Their location would be toward the back
part of the board, to the right. They are the last two in a column (in
relation to the back) of similar-sized chips, most of which are direct
soldered to the board. I can take a photo if one is needed
A stock 8032 has "expansion ROM" sockets - it was common for PET
owners to enhance their PETs with after-market firmware. I myself had
the PAICS BASIC Toolkit, the Rabbit tape speeder, a very nice enhanced
Machine Language Monitor (MICRO-MON?) and I'm blanking on what was in
my third ROM socket (BASIC 2.0 had 3 available sockets).
It's likely your PET just has no add-on firmware, but I suppose it's
possible that it _has_ add-on firmware but is missing two other ROMs,
just not as likely.
-ethan
2:53 p.m.
Okay, thanks for clearing that up.
First off, I suppose I need to check voltages.
On Tue, Aug 18, 2009 at 4:41 PM, Ethan Dicks <ethan.dicks at gmail.com> wrote:
On Tue, Aug 18, 2009 at 4:33 PM, Joe
Giliberti<starbase89 at gmail.com>
wrote:
I have a good DMM available, as well as a scope.
Good start.
I just noticed that there are two chips missing,
which appear to be ROMs.
There are sockets, but no chips. Their location would be toward the back
part of the board, to the right. They are the last two in a column (in
relation to the back) of similar-sized chips, most of which are direct
soldered to the board. I can take a photo if one is needed
A stock 8032 has "expansion ROM" sockets - it was common for PET
owners to enhance their PETs with after-market firmware. I myself had
the PAICS BASIC Toolkit, the Rabbit tape speeder, a very nice enhanced
Machine Language Monitor (MICRO-MON?) and I'm blanking on what was in
my third ROM socket (BASIC 2.0 had 3 available sockets).
It's likely your PET just has no add-on firmware, but I suppose it's
possible that it _has_ add-on firmware but is missing two other ROMs,
just not as likely.
-ethan
3:54 p.m.
On Tue, Aug 18, 2009 at 5:53 PM, Joe Giliberti<starbase89 at gmail.com> wrote:
Okay, thanks for clearing that up.
First off, I suppose I need to check voltages.
Good place to start.
If your PET is mostly working, you are likely to see some form of
stationary video garbage when you power it up, or possibly a TIM
register dump, rather than the ROM banner telling you what version of
BASIC you have and how much RAM. Oh, wait... it's an 8032... in older
PETs, the video circuit is TTL and does not require any CPU activity
to start displaying the contents of video RAM... yours has a 6545 CRTC
"video chip" (similar to what was on the original IBM PC monochrome
video card). It does need to be fed some constants from ROM by the
CPU at startup, so perhaps you'd see a blank screen unless the CPU was
running and able to fetch code from ROM.
Check your voltages for sure, especially the 7905 -5VDC regulator near
the RAM field. Those 4116s are triple-voltage. Pretty much
everything else (except the cassette motor) is +5V-only.
I've only seen one ROM chip go bad ever, so if your PET won't fire up
far enough to reset the video chip, it's probably either bad RAM or
bad address logic or a data or address bus buffer. If you are tracing
that far into it, you will probably want that scope set up.
-ethan
5:14 p.m.
I just noticed something inside the PET, so just for the moment, voltage is
on hold (though related.) There are only two wires coming off the
transformer that go to the monitor, and both seem to be 24 gauge. Not big
enough, I would think, to bring power to a CRT.
On Tue, Aug 18, 2009 at 6:54 PM, Ethan Dicks <ethan.dicks at gmail.com> wrote:
On Tue, Aug 18, 2009 at 5:53 PM, Joe
Giliberti<starbase89 at gmail.com>
wrote:
Okay, thanks for clearing that up.
First off, I suppose I need to check voltages.
Good place to start.
If your PET is mostly working, you are likely to see some form of
stationary video garbage when you power it up, or possibly a TIM
register dump, rather than the ROM banner telling you what version of
BASIC you have and how much RAM. Oh, wait... it's an 8032... in older
PETs, the video circuit is TTL and does not require any CPU activity
to start displaying the contents of video RAM... yours has a 6545 CRTC
"video chip" (similar to what was on the original IBM PC monochrome
video card). It does need to be fed some constants from ROM by the
CPU at startup, so perhaps you'd see a blank screen unless the CPU was
running and able to fetch code from ROM.
Check your voltages for sure, especially the 7905 -5VDC regulator near
the RAM field. Those 4116s are triple-voltage. Pretty much
everything else (except the cassette motor) is +5V-only.
I've only seen one ROM chip go bad ever, so if your PET won't fire up
far enough to reset the video chip, it's probably either bad RAM or
bad address logic or a data or address bus buffer. If you are tracing
that far into it, you will probably want that scope set up.
-ethan
6:39 p.m.
On Tue, Aug 18, 2009 at 8:14 PM, Joe Giliberti<starbase89 at gmail.com> wrote:
I just noticed something inside the PET, so just for
the moment, voltage is
on hold (though related.) There are only two wires coming off the
transformer that go to the monitor, and both seem to be 24 gauge. Not big
enough, I would think, to bring power to a CRT.
Sure they are... they go to a 7812 to power the entire CRT assembly,
and that won't pass more than an amp.
-ethan
7 p.m.
All right, just making sure. On to voltage...
On Tue, Aug 18, 2009 at 9:39 PM, Ethan Dicks <ethan.dicks at gmail.com> wrote:
On Tue, Aug 18, 2009 at 8:14 PM, Joe
Giliberti<starbase89 at gmail.com>
wrote:
I just noticed something inside the PET, so just
for the moment, voltage
is
on hold (though related.) There are only two
wires coming off the
transformer that go to the monitor, and both seem to be 24 gauge. Not big
enough, I would think, to bring power to a CRT.
Sure they are... they go to a 7812 to power the entire CRT assembly,
and that won't pass more than an amp.
-ethan
22 Aug
22 Aug
1:12 p.m.
Another thing. IIRC all 8000-series PETs have the speaker connected to
CB2 of the 6522 chip, and it should sound "tweet-tweet" when you power
on. Do you get any sound?
An awful lot has to be working for that to happen, so "no" is not a very
helpful answer, but if you do get the tweets, you can concentrate on the
video circuitry and the monitor.
Philip.
Joe Giliberti wrote:
All right, just making sure. On to voltage...
On Tue, Aug 18, 2009 at 9:39 PM, Ethan Dicks <ethan.dicks at gmail.com> wrote:
On Tue, Aug 18, 2009 at 8:14 PM, Joe
Giliberti<starbase89 at gmail.com>
wrote:
I just noticed something inside the PET, so just
for the moment, voltage
is
on hold (though related.) There are only two
wires coming off the
transformer that go to the monitor, and both seem to be 24 gauge. Not big
enough, I would think, to bring power to a CRT.
Sure they are... they go to a 7812
to power the entire CRT assembly,
and that won't pass more than an amp.
-ethan
18 Aug
18 Aug
4:32 p.m.
On Tue, 18 Aug 2009, Joe Giliberti wrote:
I have a good DMM available, as well as a scope.
I just noticed that there are two chips missing, which appear to be ROMs.
There are sockets, but no chips. Their location would be toward the back
part of the board, to the right. They are the last two in a column (in
relation to the back) of similar-sized chips, most of which are direct
soldered to the board. I can take a photo if one is needed
PETs have "option ROM" sockets, so it's reasonable to have one with a
couple of empty sockets.
g.
--
Proud owner of F-15C 80-0007
http://www.f15sim.com - The only one of its kind.
ScarletDME - The red hot Data Management Environment
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http://www.scarletdme.org - Get it _today_!
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23 comments
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participants (7)
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alexandre-listas＠e-secure.com.br -
ard＠p850ug1.demon.co.uk -
bfranchuk＠jetnet.ab.ca -
ethan.dicks＠gmail.com -
geneb＠deltasoft.com -
philip＠axeside.co.uk -
starbase89＠gmail.com