ZAltair Z80c #2 Fails ...

[Walt Perko]

Hi, 

I checked the voltage on chips on the Don Caprio mini-Front Panel ... I see 5.02V d.c. so that's not the issue.  The power is coming from a switching regulator rather than a 7805.  

The regulator is a: PSU3

https://ezsbc.shop/products/psu3-5-36v-to-5v-1amp-three-pin-regulator

This photo is holding STOP + RESET:  

This photo is what LEDs are ON after I release the STOP + RESET:  

When I try to EXAMINE and EXAMINE NEXT ... the address LEDs never change, that's the same when I try to DEPOSIT and DEPOSIT NEXT.  I never see anything occur on the address LEDs.  

Seems I cannot EXAMINE any address.  

.

[Walt Perko]

Hi, 

I double checked the resistor networks to be 220Ω ... basically I think they should be okay for the LEDs ... but some of the LEDs are very dim during the STOP + RESET ... so I'm not sure what is causing that, but I think it might have something to do with why the rest of the mini-Front Panel doesn't work.  

.

[Walt Perko]

Hi,  

This is the results from chip testing ... the only chips I can't test with my RLG Tauntek Chip Tester are the 74LS123's and the 8212 ... 

> 74LS107
Found 74LS107 in our database

> T
Vss pin current with only pulldowns enabled is ~0.0 mA 

Checking inputs for shorts or leakage... 

Input levels look OK with voltage dividers applied 

Checking input connections...

Input pin  4 may have a bad connection: 0.19

Input pin 11 may have a bad connection: 0.20

Logic test:

Testing thresholds: VOHmin >= 3.20, VOLmax < 0.35

Inputs:               Clks:      Outputs:

 1  4 13  8 11 10  12  9         3       2       5       6

 1  L  H  L  H  H  L   I  I      L/0.10  H/3.20  L/0.10  H/3.17

 2  L  L  H  L  L  H   N  N      L/0.08  H/3.19  L/0.09  H/3.17

 3  H  L  H  H  L  H   N  N      H/3.20  L/0.09  H/3.17  L/0.09

 4  L  H  H  L  H  H   N  N      L/0.09  H/3.20  L/0.09  H/3.17

 5  H  H  H  H  H  H   N  N      H/3.19  L/0.10  H/3.16  L/0.10

Tests failed

> T

Vss pin current with only pulldowns enabled is ~0.0 mA

Checking inputs for shorts or leakage...

Input levels look OK with voltage dividers applied 

Checking input connections... 

Input pin  4 may have a bad connection: 0.19

Input pin 11 may have a bad connection: 0.20 

Logic test: 

Testing thresholds: VOHmin >= 3.20, VOLmax < 0.35 

Inputs:               Clks:      Outputs:

 1  4 13  8 11 10  12  9         3       2       5       6

 

 1  L  H  L  H  H  L   I  I      L/0.10  H/3.19  L/0.10  H/3.17

 2  L  L  H  L  L  H   N  N      L/0.09  H/3.19  L/0.08  H/3.16

 3  H  L  H  H  L  H   N  N      H/3.19  L/0.09  H/3.17  L/0.09

 4  L  H  H  L  H  H   N  N      L/0.09  H/3.19  L/0.09  H/3.17

 5  H  H  H  H  H  H   N  N      H/3.19  L/0.10  H/3.16  L/0.10

Tests failed

> T

Vss pin current with only pulldowns enabled is ~0.5 mA 

Checking inputs for shorts or leakage... 

Input levels look OK with voltage dividers applied 

Checking input connections... 

Input levels look OK with pulldowns applied 

Logic test: 

Testing thresholds: VOHmin >= 3.20, VOLmax < 0.35 

Inputs:               Clks:      Outputs: 

 1  4 13  8 11 10  12  9         3       2       5       6

 1  L  H  L  H  H  L   I  I      L/0.19  H/3.27  L/0.19  H/3.26

 2  L  L  H  L  L  H   N  N      L/0.18  H/3.26  L/0.18  H/3.25

 3  H  L  H  H  L  H   N  N      H/3.27  L/0.20  H/3.27  L/0.19

 4  L  H  H  L  H  H   N  N      L/0.19  H/3.26  L/0.18  H/3.26

 5  H  H  H  H  H  H   N  N      H/3.27  L/0.20  H/3.28  L/0.20

Tests passed, chip looks OK

>