I recently received a Viewmaster 80 (AE) card, and when I insert it into a slot, the system refuses to boot, and gives a repeating click from the speaker. Have any of you see that before? I am tempted to swap the PROMs, but I'm not sure if that is where the problem exists.
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Are you saying that with the card inserted, the system just produce clicking sound when power is applied?
If that's the case, I think it's not a ROM problem but other HW problem since working card wouldn't even be active unless explicitly enabled.
Correct. The prior owner swears up and down that it worked when they tested it, but they used no ESD protection and posted it in standard bubble packing plastic, so anything could have been damaged, I would prefer to get it working, rather than returning it, as I prefer that card to the Videx due to the internal softswitch functions.
I personally expect a 74-series chip dying, but I'm unsure. I have another dead AE VM80 to use to borrow parts w/o this issue, but that does nothing on PR#3, so I may try to swap one chip at a time on a test board to see if I can isolate the bad components.
Is VM80 the only card installed? autostart rom does scan all the expansion roms for bootable expansion card.
if you have it installed in traditonal slot 3 and a disk II interface in slot 6, does the system still do that funny thing you mentioned?
I know you know better... but is the clicking sound really coming from the speaker? Or is it the power supply shutting down? Sounds more like a short somewhere on the card. Check those caps!
The power supply is fine. I normally have a genuine Viex car in Slot 3, an I swapped it out for the Viewmaster to run the test. Slots 0, 2, 4, and 6 are occupied by a Language card, a serial card, a Z80 Softcard, and a Disk II controller with two drives.
The VM80 had the same issue with all cars, with only the Disk ][ card, and by itself. Power consumption was my first suspect, but it can't be that, as the VM80 doesn't draw more power on its own that all of this at once.
As I sadi, I suspect component failure on te VM80. it could easily be an internally shorted IC, or it could be the VM80 EPROMs. The card itelf isn't horribly complicated.
My reason for wanting the VM80 is how it handles passthrough and mode-switching. I do have another (nonworking) MV80 board to use for spares, s I may try that as a parts source. (The other card never enters 80 column mode on PR#3, but otherwise does not do anything naughty, s it may simply have bad EPROMs, as it has been through hell and back).
Something important to note, is that no vieo output is ever displayed on the CRT. I didn't use a scope to see if the VM80 is putting out a signal, because I din't leave the system on with it installed for more than a few seconds. As soon as I hard the clicking, which assuredly is coming from the speaker, trying to issue a system beep repeatedly, I turned it off, and my additional power on tests have all been under 4 seconds to minimise possible damage. My future tests will be on a test mainboard.
My first test will be without the AE ROMs, to eliminate them as a culprit. Then, I will strip components one at a tiime. If it doesn't lock up with the ROMs removed, then they are probably corrupt, but if it doesn't, then I can test those on my other VM80. From there, the 465055 is my next maor component.
You can view the card here:
In that image, you can see that there is a primary ROM wired direct to the exp slot pins that, if corrupt or shorted, might be the issue, as well as a 74LS199 chip. I do nt immediatel recognise the 199 chip, and I don't see datasheets for it readily, so I am uessing that it is a binary counter, but I need to look at the actual IC with my glasses and a lens to see if that number is correct.