TT030 Diagnostic Cart Help

[grunwald]

I am currently on a quest to resurrect a pair of TT030s. Both had torn pins/pads on the CPUs (a story for another day), as well as other underlying issues. I managed to repair the pads and install new CPUs in both units. The first unit had 23 missing pads which I sucessfully repaired. This unit now boots without error on both floppy and HD, with or without added memory boards. The only remaining issue is when I try to boot with a diagnostic cart, the unit halts the CPU without any output to the screen or RS232. I have a 3rd working TT030 which the cart works perfectly on. Any ideas on what might cause this behavior? I'll get into the 2nd unit once I figure this one out.... Thanks!

[frank.lukas]

There is a Fuse on the Cartridge Port ...

[grunwald]

Thanks Frank! Not sure if that is the issue yet, but the fuse is definitely blown. It's one of the black ones so you can't tell from just looking. I'll have 20 of them on Wednesday and let you know...

[grunwald]

Thanks again Frank. You were dead on with the fuse. I replaced it and now the diag cart works perfectly. I am going to start a new topic to discuss my last non-working TT. I replaced the CPU, but can not get anything on the monitor or rs232 when the diag cart is in. The cpu is not halted and I have activity coming from the cart on the high data lines. I believe I may have a bad DMAC but I'm not sure how to check it definitively. There is no data output from there to the DCU. If I boot without the diag cart, I get data across the whole bus for a second with jailbars on the monitor, then the cpu halts. I am waiting on an additional probe adapter for my logic analyser so I can read the entire bus. Thanks again...

[frank.lukas]

May be RAM problems with the RAM or the MCU U206 ?

See the Service Manual at ...
https://docs.dev-docs.org/