faulty model 4

[daafies]

In the meantime ill resolder some of the sockets/ICs we talked about

 

 

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[daafies]

In the meantime ill resolder some of the sockets/ICs we talked about

 

 

Sent from my iPhone using Tapatalk

ah well no luck either. bummer!

[JamesD]

Have you tried touching the RAM chips like I suggested? Any hot ones?

[daafies]

Have you tried touching the RAM chips like I suggested? Any hot ones?

 

hi James, yes i did. i replied sunday. there were plenty messages goingn round, so it was easy to miss. there were couple hot ICs but none were the RAM chips. i measure the temps as well

 

here it is:

 

Posted Sun Jun 28, 2015 7:31 PM

after running for ~15mins:

 

z80 = 130F

PALl6L8 (U59) = 129F

PAL16R6A (U3) = 120F

PALl6L8 (U4) = 120F

MCM68A316E Character Generator (U23) = 122F

 

ram chips are 95F ish (not hot to the touch)

 

all other chips under 120

[daafies]

update: i also replaced the u21 with a 'new' chip from ebay, but no difference. i guess the leaves the ROMs and PALs. i'm in contact with a gentleman called Ian in Australia. he might have a spare board

[Turbo-Torch]

If anyone can help you, he can.

 

In your first post, you mentioned the power supply issue. Are you still using it after the cap failure? Have you checked the voltages under load?

 

The one that goes off like a firecracker with a big smoke show is the .1 uF X-Capacitor. Mine let go Friday in a big way.

http://www.digikey.com/product-search/en?keywords=399-7483-ND

$1.77 at Digi-Key and then choose 1st class for shipping which was about $3.80 for me. Ordered it Friday and it was in my mailbox on Monday...impressive considering it was 4th of July weekend too.

[daafies]

Yea i replaced both the .22 and .01 (if i remember the values correctly) Measured and voltages look ok . +11.97 , -11.99, 4.98. ish. I used an atx power supply at some point also. No difference.

 

I like Digikey also, but jameco is close to my home so i can so will call

 

 

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[daafies]

update! i got Ian's board in the mail, and narrowed the problem down to the roms in U68 and U70. rom a and rom c if i'm not mistaken.

 

now, without the fdd board attached i get the CASS? prompts and i can go into basic. YAY!

 

but, (of course) with the floppy controller attached, i do not get the "diskette" prompt. just a blank screen. the drive spins up tho. pressing break and reset i can go into basic again and do "out 244,1" and disk 0 spins up again. so it can access it ok it seems.

 

i dont have a floppy to try, but i can hook up the HxC floppy emulator to see what happens.

 

am i supposed to see the diskette promt?

 

PS Ian did mention, and i can confirm, when in model 3 basic the cursor does not blink. so there could still be some other an issue with the ROMs

 

thanks!

david

[daafies]

Spoke to Ian, and apparently earlier model 4s had a bug that prevented the diskette? prompt to be displayed. Inserting a floppy without closing the door does cause a diskette? prompt:)

 

Now on to install the HxC

 

 

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[daafies]

yay i can boot trsdos of the HxC i took out the old drives for now and hooked the HxC to the internal port.

 

i wanted to try to test the external drives by attaching them to the external port, but trsdos does not see them. in basic i can "out 244,X" ok.

 

i assume the internal port is drives 1 and 2 (order decided by cable?) and external port is drive 3 and 4?