The famous grey screen black frame issue.

[Rabs]

Current draw from power on 942mA.

[oyshals]

Current draw from power on 942mA.

Hmmm... Mine was above 1,1 last time I checked, will re-check.

[oyshals]

Current draw from power on 942mA.

Hmmm... Mine was above 1,1 last time I checked, will re-check.

So, I re-checked the int on my ga and z80. I had to adjust my scope to "full sensitivity" (sorry not familiar with the terms) to find anything. I was only able to find 200mV. Since I had adjusted the scope in this way, I'm guessing this is just static, so looks like it's pulled low as I can see that you have 5V. I will watch again the two last videos you posted as these explained the int signal very well.

Also noticed that I have to reflow pins on the contact for power switch. Probably because I've connected and disconnected so many times.

[Rabs]

So yes a low INT was one of the symptoms in Noel's video.

His Diag ROM did not work because of the edge connector but you have cleaned and cleaned yours. I continue to have problems with edge connectors and often have to reseat the connector.

But assuming it is good then something is stopping the Diag ROM from running. He indicates it only depends on ROM not RAM but also refers to the data latch buffer IC114. So inference is something is corrupting the data bus. @Bryce and @eto have already suggested removing the ROMs and retrying the Dandanator. But in case somehow the latch buffer is placing RAM on the bus and as you have these socketed anyway you could try removing all RAM and retrying the Dandanator.

[oyshals]

That's helpful I will do another try with the edge connector, and remove all chips on ram bank 0 before desoldering more.

Might be a stupid question for you with more experience, but are you suggesting removing both the 40015 and 40025 roms? And a follow up stupid question; which of these are upper and lower rom? I've seen those terms being used alot.

[eto]

40015 is a 16K EPROM with AMSDOS( upper ROM #7)
40025 is a 32K EPROM with Firmware (lowerROM) in the lower 16K and BASIC (upper ROM #0) in the upper 16K

When the CPC is switched on or reset the firmware (the lower ROM) is entered at address &0000, BASIC (or other upper ROMs) will be accessed at &C000. Some logic in the CPC will make sure that the the 40025 can act as two ROMs at different addresses.  

[Rabs]

I think @Bryce and @eto are only referring to the lower ROM, 40025, which occupies the lower address space where the DIAG ROM runs but hopefully they will correct me if wrong. But what I don't understand is, if the ROM is an issue why the CRTC is being correctly initialised in terms of HSYNC and VSYNC.

[Rabs]

So yes a low INT was one of the symptoms in Noel's video.

His Diag ROM did not work because of the edge connector but you have cleaned and cleaned yours. I continue to have problems with edge connectors and often have to reseat the connector.

But assuming it is good then something is stopping the Diag ROM from running. He indicates it only depends on ROM not RAM but also refers to the data latch buffer IC114. So inference is something is corrupting the data bus. @Bryce and @eto have already suggested removing the ROMs and retrying the Dandanator. But in case somehow the latch buffer is placing RAM on the bus and as you have these socketed anyway you could try removing all RAM and retrying the Dandanator.

That's helpful I will do another try with the edge connector, and remove all chips on ram bank 0 before desoldering more.

I think you only need to worry about the lower active RAM bank.

[oyshals]

So yes a low INT was one of the symptoms in Noel's video.

His Diag ROM did not work because of the edge connector but you have cleaned and cleaned yours. I continue to have problems with edge connectors and often have to reseat the connector.

But assuming it is good then something is stopping the Diag ROM from running. He indicates it only depends on ROM not RAM but also refers to the data latch buffer IC114. So inference is something is corrupting the data bus. @Bryce and @eto have already suggested removing the ROMs and retrying the Dandanator. But in case somehow the latch buffer is placing RAM on the bus and as you have these socketed anyway you could try removing all RAM and retrying the Dandanator.

That's helpful I will do another try with the edge connector, and remove all chips on ram bank 0 before desoldering more.

I think you only need to worry about the lower active RAM bank.

Thanks! That is the right one yes? If not, I've been wasting your time for months now 🙈

[eto]

Thanks! That is the right one yes? If not, I've been wasting your time for months now 🙈

yes, the right bank is bank 0.

However: if there is a short on any IC on bank 1, this will have the same impact as a short on bank 0. The lines are fully parallel (except for CAS). 

[Bryce]

I think @Bryce and @eto are only referring to the lower ROM, 40025, which occupies the lower address space where the DIAG ROM runs but hopefully they will correct me if wrong. But what I don't understand is, if the ROM is an issue why the CRTC is being correctly initialised in terms of HSYNC and VSYNC.

Both ROM's are connected in parallel for most pins, so either ROM being bad will give you problems.

Bryce.

[oyshals]

Removed the lower rom, 40025, turned it on, and got a blank (black) screen. (as expected since there was no rom)

Connected the Dandanator and turned it on again (not pressing the diagnosis button) and got a grey screen with black frame.

Restarted with diagnosis button pressed, same as before blank/black screen. So either something is wrong with my Dandanator, or something is interrupting this specific ROM. Have both cleaned and measured the expansion port.

I'm a bit baffled. Will start measuring before putting in a socket for the lower ROM. Also maybe try replacing the socketed chips without ROM installed.

[oyshals]

Does anyone have any information on the IC201? I can't seem to find it in the main schematics.

Mine gets very hot, and when I touch it, I get disturbance on the screen. I've reflowed all its pins.

I searched on the forum and found that this was part of the issue on two incidents with the grey screen black frame case.

[robcfg]

According to the service manual parts list, IC201 is the upd765 floppy drive controller.

Edit: You can see the schematic of the disk controller part on page 28 of the pdf service manual, with the title "Interface Circuit Diagram".

[oyshals]

According to the service manual parts list, IC201 is the upd765 floppy drive controller.

Thanks. It's showing strange symptoms, and I need to add that the CPC was put away due to inability to read discs. Could be something to look into then...

[robcfg]

Maybe the chip itself isn't bad, though if it gets super hot it's definitely a bad sign, so please check the components associated with it.

Remember, page 28 of the pdf service manual, Interface Circuit Diagram 

[oyshals]

Maybe the chip itself isn't bad, though if it gets super hot it's definitely a bad sign, so please check the components associated with it.

Remember, page 28 of the pdf service manual, Interface Circuit Diagram 

Thanks! Found it, my bad 😅

[robcfg]

No worries mate, good luck with the repair!

[Audronic]

Does anyone have any information on the IC201? I can't seem to find it in the main schematics.

Mine gets very hot, and when I touch it, I get disturbance on the screen. 

@oyshals 
Also touch the 3 other chips above IC201
These are IC206 - IC203 - IC208

I had a weird fault a long time ago similar to touching chips in that area
and it turned out to be the IC203 (74HC240N)
Slide your Finger Left and Right over each chip and Observe the screen

Good luck

Keep Safe

Ray

[oyshals]

Does anyone have any information on the IC201? I can't seem to find it in the main schematics.

Mine gets very hot, and when I touch it, I get disturbance on the screen.

@oyshals
Also touch the 3 other chips above IC201
These are IC206 - IC203 - IC208

I had a weird fault a long time ago similar to touching chips in that area
and it turned out to be the IC203 (74HC240N)
Slide your Finger Left and Right over each chip and Observe the screen

Good luck

Keep Safe

Ray

Thanks! Did that and only got a reaction from ic201. I was pretty rough with the other ones, but no reaction. Will look for signals later.

[Rabs]

I have not had problems with IC 201 the disk controller but I have with the associated logic gates (actually the tracks) which resulted in ROMDIS being asserted incorrectly when A15 was high (it actually stopped the BASIC ROM from running). It is worth checking the logic gate outputs in this area and look for any floating signals or outputs which do not match the logic inputs.

[oyshals]

I have not had problems with IC 201 the disk controller but I have with the associated logic gates (actually the tracks) which resulted in ROMDIS being asserted incorrectly when A15 was high (it actually stopped the BASIC ROM from running). It is worth checking the logic gate outputs in this area and look for any floating signals or outputs which do not match the logic inputs.

Thanks, I'll do that.

I also think i'll have to start over again.

I tend to loose track after a week off 🙈

[Rabs]

I had a broken track between IC205 and IC212 on the Disk Controller side of the PCB. 

IC205 PIN 2 AND gate input was floating high, should have been held low by IC212 PIN 5.
IC205 PIN 1 AND gate input is connected to A15
IC203 PIN 3 AND gate output is connected to ROMDIS

Every time A15 went high, the ROM was disabled. 

So lower ROM worked, upper ROM was disabled. Took me a while...

Worth a check in case you have something similar as this stopped the ROM code from running.

[Rabs]

By the way, in the end I did purchase a Dandanator. First time I plugged it in and powered on I got a grey screen black border and this is with a fully working 6128. I cleaned the edge connector and reseated the Dandanator and it worked fine. An alternative to using the Dandanator to run the Diag ROM is to just replace the lower ROM with a Diag ROM. 

[oyshals]

By the way, in the end I did purchase a Dandanator. First time I plugged it in and powered on I got a grey screen black border and this is with a fully working 6128. I cleaned the edge connector and reseated the Dandanator and it worked fine. An alternative to using the Dandanator to run the Diag ROM is to just replace the lower ROM with a Diag ROM.

Is there somewhere I can buy a Diagnostics rom online, or do most people make them themselves?

I'm looking seriously at buying a working 6128 from eBay for comparison as there seems to be alot of issues that could cause the grey screen.

My voltage is also somewhat unstable, sometimes as low as 4,65v and up to 4,95v, and sometimes it uses a long time starting up, which has turned my attention a bit towards dried out capacitators, but there's probably about 80 of them, so that would be quite a task. However, I've found 2 or 3 which has cracks (orange ones next to the ram banks) but no shorts in them.