Thanks guys.
The testing I've done thus far was as per this article
viewtopic.php?t=7185
This is a machine I haven't touched since pre-covid (can't imagine why I was busy then). It's the one machine that I can't remember where on earth I got it from, or when. Similarly, I can't remember if it came with Econet pre-fitted or I've done it myself (the 3 machines which I know I've personally upgraded are all working fine).
It's an Issue 4 Model B (not upgraded A), with the (still unsolved, seemingly impossible) ROM issues that I've mentioned over the past few days.
S2 is definitely unmade, with no continuity even with the meter on 60M range.
It does have an Opus DDOS board fitted, which I've not tried - I'll put it on the to-do list.
I've already tried swapping the 75159 and 68B54 with those from a working machine - no difference.
The machine is connecting to one of Ken Lowe's Pi Econet bridges, with hub extension board. Termination is as Ken supplied it. So far, the bridge has worked fine with 2 Model Bs, a B+, Master 128, Master ET, and an A3020.
Only one machine is ever connected to the bridge during testing, so there's no interference from other stations.
Just to be sure, I've also tried it with a real Filestore; same result.
With respect to the resistors I've checked, they were done as per the quoted article. The abnormal results (with bracketed results from a working machine) are:
R36 2.9K (10K)
R41 2.0K (100K)
R34 2.0K (9K)
R35 2.0K (9K)
R40 4.9K (100K)
Removing all the Econet ICs didn't change the values.
Moving onto the voltages...
Without the bridge connected:
With IC93 in, pin 12= 2.0V, pin 13=2.0V (0.01V difference)
IC93 removed, pin 12=2.0V, pin 13=2.0V
With the bridge connected:
IC93 in, pin 12=2.64V, pin 13=2.15V (0.49V difference)
IC 93 out, pin 12=2.64V, pin 13=2.15V
As previously mentioned, the resistance between pins 12/13 and either 0V or 5V is only around 5K. On a working comparison, it's about 108K.
The testing I've done thus far was as per this article
viewtopic.php?t=7185
This is a machine I haven't touched since pre-covid (can't imagine why I was busy then). It's the one machine that I can't remember where on earth I got it from, or when. Similarly, I can't remember if it came with Econet pre-fitted or I've done it myself (the 3 machines which I know I've personally upgraded are all working fine).
It's an Issue 4 Model B (not upgraded A), with the (still unsolved, seemingly impossible) ROM issues that I've mentioned over the past few days.
S2 is definitely unmade, with no continuity even with the meter on 60M range.
It does have an Opus DDOS board fitted, which I've not tried - I'll put it on the to-do list.
I've already tried swapping the 75159 and 68B54 with those from a working machine - no difference.
The machine is connecting to one of Ken Lowe's Pi Econet bridges, with hub extension board. Termination is as Ken supplied it. So far, the bridge has worked fine with 2 Model Bs, a B+, Master 128, Master ET, and an A3020.
Only one machine is ever connected to the bridge during testing, so there's no interference from other stations.
Just to be sure, I've also tried it with a real Filestore; same result.
With respect to the resistors I've checked, they were done as per the quoted article. The abnormal results (with bracketed results from a working machine) are:
R36 2.9K (10K)
R41 2.0K (100K)
R34 2.0K (9K)
R35 2.0K (9K)
R40 4.9K (100K)
Removing all the Econet ICs didn't change the values.
Moving onto the voltages...
Without the bridge connected:
With IC93 in, pin 12= 2.0V, pin 13=2.0V (0.01V difference)
IC93 removed, pin 12=2.0V, pin 13=2.0V
With the bridge connected:
IC93 in, pin 12=2.64V, pin 13=2.15V (0.49V difference)
IC 93 out, pin 12=2.64V, pin 13=2.15V
As previously mentioned, the resistance between pins 12/13 and either 0V or 5V is only around 5K. On a working comparison, it's about 108K.
Statistics: Posted by Boydie — Thu Nov 14, 2024 9:15 am