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is not clear to me: prachoeha?

Dear echo subscribers, at the request of one person from Astrakhan, who
loves the spectrum, I am posting his cry for help here.

--------------------Original Message ----------------------------
Hello! I am a beginner spektrumist from Astrakhan! My name is Revin
Denis Evgenievich. My email: denis...@gmail.com

I have a problem with the spectrum! Anyone who can, please help me in any way, otherwise I'm completely clueless about hardware.

I got a Pentagon-128 (model 1991, with VG93, without AY). In the panels
there is only a processor and a VGshka. 3 ROM chips (two soldered to each other
27256) and RF2.
Connected it to an EGA monitor. The image is clearly visible (just shifted,
but that doesn’t matter for now).

Problem:
When I turn on the spectrum, only colored flashing
colored cubes appear. That's all. When I press reset, the cubes change.

What was done next:
- the VG-shka was pulled out (so as not to get in the way in vain)
- I tried to move various components. And _attention!_ the initial
menu (selecting boot, BASIC, TDPOS) rarely appeared! It was possible
even to select a menu item from the keyboard!
- the board was inspected for defects, cracks

Data:
- it was not possible to find what I did exactly to make the menu appear. That is, I cannot reproduce exactly the appearance of the menu. I don’t know what I touched
or moved to make it appearmenu (it seemed like every time the menu appeared due to different
components).
- I examined the board: in some places on the board the tracks were “cut”,
probably by those who used this spectrum before me. Here and there a couple of wires are soldered on the back side of the board. It was not possible to find cracks and
broken legs of m/sx, capacitors, resistances!
The tracks do not seem to be closed.

Please help, maybe any advice? Thank you very much in advance!
I'm desperate. I don’t even know what to do. I don't
know how to work with an oscillograph (and it doesn't seem to work for us).
Thank you!

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Let's not leave a person in trouble, let's at least help with advice. Write to his e-mail address, or if anyone doesn’t have Internet, write to me, I’ll pass it on. You can use no soap so as not to inflate the traffic.

Bye

AB> Please help, maybe any advice? Thank you in advance
AB> very much!
AB> I'm desperate. I don’t even know what to do. I don't
AB> know how to work with an oscilloscope (and it doesn't seem to work for us).
AB> Thank you!

This is the key point here IMHO!...

If he still manages to turn on the oscilloscope and poke the probe in turn on
each of the data lines directly on the processor and then on ROMs, then he should
see the same picture everywhere (in In this case, for sure on some line
the picture will either be a “flat line” or sharply different from other lines
of the data...). If differences are found, then you will need to reconsider this entire
line for breaks/unnecessary connections.

If this does not help, then you need to look at the address bus there, of course, the signal between the lines will not be as “identical” as on the data bus, but I think a “suspiciously
crooked” signal can be identified intuitively (the differences will be obvious).
:)))

I hope I explained it by lamer...

Regards.

June 15, 05 _Andrey Baglay_ wrote *All 'y* on the topic: ""

AB> Hello! I am a beginner spektrumist from Astrakhan! My name is Revin
AB> Denis Evgenievich. My email: denis...@gmail.com

AB> I have a problem with the spectrum! Anyone who can, please help me in any way, otherwise
AB> I'm a complete zero in hardware.

AB> I got a Pentagon-128 (model 1991. With VG93, without AY). In the panels
AB> there is only a processor and a VGshka. 3 ROM chips (two soldered to each other
AB> 27256) and RF2.
AB> Connected it to an EGA monitor. The image is clearly visible (only shifted,
AB> but that doesn’t matter for now).

AB> Problem:
AB> When I turn on the spectrum, only colored flashing
AB> multi-colored cubes appear. That's all. When I press reset, the cubes change.

AB> What was done next:
AB> - the VG-shka was pulled out (so as not to interfere in vain)
AB> - I tried to move various components. And _attention!_ the initial
AB> menu (selecting boot, BASIC, TDPOS) rarely appeared! You could
AB> even select a menu item from the keyboard!
AB> - the board was inspected for defects, cracks

AB> Data:
AB> - I couldn’t find what I did exactly to make the menu appear. That is
AB> I cannot reproduce exactly the appearance of the menu. I don't know what I amI touched
AB> or moved it so that the menu appeared (it seems that every time because of different
AB> menu components appeared).
AB> - I examined the board: in some places on the board the tracks were “cut”,
AB> probably to those who used this spectrum before me. Here and there
AB> a couple of wires are soldered on the back side of the board. It was not possible to find cracks and
AB> broken legs of the m/sx, capacitors, resistances!
AB> The tracks do not seem to be closed.

AB> Please help, is there any advice? Thank you
AB> very much in advance! I'm desperate. I don’t even know what to do. I don’t know how to work with
AB> an oscilloscope (and it doesn’t seem to work for us).
AB> Thank you!

Look at all the solder points on the board and suspicious places (or all points are possible) with an x3.5 watch magnifying glass. As a rule, performance is restored if
all elements are in working order. Desolder suspicious microcircuits and replace them with new ones.
To desolder a microcircuit, first remove the solder using suction from each soldering point
m/s, and then use tweezers to pry it under one side of the m/s with some force and
heat the soldering points with a soldering iron, moving it from point to point to until this side comes off. You unsolder the second side of the m/s in the same way. The ends of the tweezers must be thin in order to pry under the edge of the m/s. By replacing the m/s
it is possible to repair it faster than to get to the bottom ofmalfunctions. To do this, you need to know very well the theory of computer operation, the passage of signals, have oscillograms
and understand them. To identify faulty m/s, I made a special stand for checking them. I unsolder it, insert it into the stand socket and check all switching modes in the reference book. I supply signals to the inputs, and at the output
the corresponding LEDs light up according to the table. It is better not to touch the memory chips, they will be revealed later, when the computer is working normally.

With best wishes, Vladimir Panteleevich.

AB>> thank you very much! I'm desperate. I don’t even know what to do.
AB>> I don’t know how to work with an oscilloscope (and it doesn’t seem to work for us
AB>>). Thank you!
AR> This is the key point here IMHO!...
I probably missed something, but I didn’t
discover the original letter for help, or maybe it didn’t reach me. What's the problem?

AB>> thank you very much! I'm desperate. I don’t even know what to do. I don’t know how to work
AB>> with an oscilloscope (and it doesn’t seem to work for us). Thank you!
Wow, it looks like the letter has been quoted in full?

VC> Using a x3.5 watch magnifying glass, look at all the solder points on the board and suspicious
VC> places (or you can solder all the points). As a rule, the performance of
VC> is restored if all elements are in working order. Unsolder any suspicious
VC> microcircuits and replace them with new ones. To desolder the microcircuit
VC>, first remove the solder using suction from each soldering point m/s, and
VC> then use tweezers to pry it under one side of the m/s with some force
VC> and heat the soldering points with a soldering iron, moving it from point to point until
VC> the side will not come off. You unsolder the second side of the m/s in the same
VC> way. The ends of the tweezers must be thin in order to pry under the edge
VC> m/s. By replacing the m/s it is possible to repair it faster than getting to the bottom of the
VC> malfunction. To do this, you need to know very well the theory of operation of the
VC> computer, the flow of signals, have oscillograms and understand
VC> them. To identify faulty m/s, I made a special stand for
VC> checking them. I unsolder it, insert it into the socket of the stand and check
VC> all switching modes in the reference book. I supply signals to the inputs, and
VC> output, the corresponding LEDs light up according to the table.
VC> It’s better not to touch the memory chips, they will be revealed later when the computer
VC> is working normally.
Yes, besides this, try (it’s me AB, of course, not VC, I just didn’t get the original
) change the processor to another one that is known to be good, maybe it’s glitching.
Then another ROM-x Get it from another Spectrum, the interference may be in the “sandwich” of the ROM. Well, then it’s a matter of fine logic and we’ll disappear everything
suspicious.

With rules, Danil aka Merlin/ULG

AB> Connected it to the EGA monitor. The image is clearly visible (only shifted,
AB> but that doesn’t matter for now).

AB> Problem:
AB> When I turn on the spectrum, only colored flashing
AB> multi-colored cubes appear. That's all. When I press reset, the cubes change.

I recently bought exactly the same classic Pentagon. I connected it to the Electronics 32 VTC 202 monitor. The problem was 1 in 1. All the memory is on the panels. So the squares disappeared and the computer started up only after all
RU5 were clearly driven into their sockets. I also have a computer Byte 48 (at least that's what it says on it). He has reliably dead memory chips.
The picture is exactly the same as it was not in the Pentagon.
I am also far from hardware, but the symptoms are the same...

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