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by kodak80
Tue Dec 03, 2019 10:23 am
Forum: MONGREL H4 USER BUILDS
Topic: kodak80 H4 build (x2)
Replies: 44
Views: 1171

Re: kodak80 H4 build (x2)

I re-checked the resistance against VCC and have updated the readings above. Nothing really changed apart from the VCC pins. All other readings were similar.
by kodak80
Mon Dec 02, 2019 9:32 pm
Forum: MONGREL H4 USER BUILDS
Topic: kodak80 H4 build (x2)
Replies: 44
Views: 1171

Re: kodak80 H4 build (x2)

Will re-check the expansion port resistance to VCC later as have to go to my day job now.
by kodak80
Mon Dec 02, 2019 9:15 pm
Forum: MONGREL H4 USER BUILDS
Topic: kodak80 H4 build (x2)
Replies: 44
Views: 1171

Re: kodak80 H4 build (x2)

75.4k: 14,49 I think you tested these to GND, not to VCC. What about the rest then? All of these are pullups, not pulldowns. You need to be testing resistance to VCC. Thanks. You are correct, these were all tested to GND. When I test these to VCC the resistance shows as a 0.3 which on my multimeter...
by kodak80
Mon Dec 02, 2019 8:27 pm
Forum: MONGREL H4 USER BUILDS
Topic: kodak80 H4 build (x2)
Replies: 44
Views: 1171

Re: kodak80 H4 build (x2)

I have run round the pins on the GLUE, MMU, 27C4096 PLCC and an expansion socket and found no shorts. I have tested 5v on all IC chips and these are good. Had to check continuity on the chips that sit under the power supply but this was also fine so assume 5v to these chips is good. Tested resistanc...
by kodak80
Sun Dec 01, 2019 8:02 am
Forum: MONGREL H4 USER BUILDS
Topic: kodak80 H4 build (x2)
Replies: 44
Views: 1171

Re: kodak80 H4 build (x2)

Thanks @PhilC I did seem to power through this one compared to the Alpha board.

Still scary turning on the power though.
by kodak80
Sun Dec 01, 2019 3:37 am
Forum: MONGREL H4 USER BUILDS
Topic: kodak80 H4 build (x2)
Replies: 44
Views: 1171

Re: kodak80 H4 build (x2)

Okay, fitted the 13 pin din video connector (not yet soldered in but fairly sure the pins are all connected to the board) along with the Falcon 4mb RAM card and powered on...... White screen, same as derkom . I have a known working Exxos 1.02/1.04 TOS ROM from one of my Alpha boards in place so it i...
by kodak80
Sun Dec 01, 2019 2:35 am
Forum: MONGREL H4 USER BUILDS
Topic: kodak80 H4 build (x2)
Replies: 44
Views: 1171

Re: kodak80 H4 build (x2)

https://www.exxoshost.co.uk/forum/posting.php?mode=quote&f=78&p=29092 exxos and Icky Just wondering the best option for the BGACK PULLUP fix if the expansion port sockets are not installed? Edit: here is the fix applied to the PLCC CPU socket along with the DTACK fix. 7E32BB05-8658-4988-BEB2-A7DF8DA...
by kodak80
Sun Dec 01, 2019 2:27 am
Forum: MONGREL H4 USER BUILDS
Topic: kodak80 H4 build (x2)
Replies: 44
Views: 1171

Re: kodak80 H4 build (x2)

After taking the photos I found that the 74LS02 IC had a bent pin not in the socket so this is now fixed. I have socketed the 32mhz OSC for now using 4 individual female pins which allows me the flexibility of using a cheap 32.0mhz OSC for initial testing and can change over to the proper OSC once I...
by kodak80
Sun Dec 01, 2019 1:45 am
Forum: MONGREL H4 USER BUILDS
Topic: kodak80 H4 build (x2)
Replies: 44
Views: 1171

Re: kodak80 H4 build (x2)

Okay, first board is built apart from external connectors. Have a Falcon 4mb RAM board to fit and also a 4mb SIMM so I can test both options (not at the same time though). Still need to run through the fixes as well. 78600DE9-C0F9-41E6-B0FF-BB6C44E7BB38.jpeg F0EF307A-1886-45F3-9E12-82FCD68ACE67.jpeg...

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