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Old 13th Mar 2023, 8:48 am   #221
3pinplug
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Default Re: Help needed with - Racal Dana 9081

No you are not wrong there i thought change a few tants and hey presto, i suspect if anyone has any probs with one in the future the answer will be in this thread. Certainly come along way and suspect we are very close now!
Can you confirm what the triangle F measurements are i had assumed that was the frequency, tried looking it up but started going down inverse triangles used in maths nothing that seemed to relate to what we are doing here, will run the tests this evening.
Thanks again for your perserverance, your knowledge of these is incredible!
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Old 13th Mar 2023, 6:20 pm   #222
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Default Re: Help needed with - Racal Dana 9081

Hello Mark,

The symbol is the Greek letter Delta, sometimes used to mean a change in maths. In this case, Delta F gives a small change in frequency. Looking at photos of the 9081, some seem not to have the Delta F position marked on the control. If your one is like that, I don't know whether you can set up the test. The position to use is one click anti clockwise from the 5kHz step position.

If it works, it should force the pulse generator to produce only one pulse per press of the switch. That should make the range 5 behaviour more predictable, I hope.

Paula
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Old 13th Mar 2023, 7:54 pm   #223
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Default Re: Help needed with - Racal Dana 9081

Hi Paula
Checked IC15 pins as follows, certainly not as expected:-
Pin 1=0.00v no change of reading throughout each band & across each range.
Pin 2= 1236v , same state as above
Pin 3= 0.00v, same state as above

Pin 11= 12.17v no change of reading throughout each band & across each range
Pin 12= 10.10v same state above
Pin13 = 0.00v same state as above

Pin 8= 0.00v
Pin9= 0.00v
Pin 10 = 0.00v
All no change of reading throughout each band and across each range

I have two unlabelled clicks anticlockwise from the 5khz setting but they are not marked delta F, from above does IC15 need replacing.
Regards
Mark
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Old 13th Mar 2023, 8:27 pm   #224
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Default Re: Help needed with - Racal Dana 9081

Hello Mark,

Maybe the first anticlockwise click is the one to use for the delta F position. That's where it is on my 9082 and on other 9081s where it is marked. It's possible that on early 9081s this function hasn't been implemented.

IC15 doesn't seem to be working. Check that pin 14 is at 11.8V and pin 7 is 0V, it's odd that all three gates are faulty otherwise.

Did you try the step switch in all its positions, because the voltages on some of the inputs should change as you rotate it? Just to be sure, the IC15 I'm talking about is on the Logic board, not the phase detector board. It should be a 4071. If that is the one you were measuring and pin 14 is at 11.8V, then it needs to be replaced.

Paula
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Old 13th Mar 2023, 10:12 pm   #225
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Default Re: Help needed with - Racal Dana 9081

Hi Paula
The IC is a CD4071BE on the 19-0842 board logic assembly,
Pin 14 of IC15 is 12.20v
Pin 7 is 0.00v
Pins1 & 3are still 0.00v on all ch spacings and up and down frequency.
Pin 2 is voltage on every ch spacing as follows:-
5khz is 10.10v
10khz is 12.36v
20khz is 11.75v
6.25khz is 10.17v
12.5khz is 12.36v
25khz is 11.73v
50khz is 11.05v
15khz is 12.36v
30khz is 11.73v
60khz is 11.05v
The above readings do not change up the band

Pin 8 0.00v allchannel spacings and no change across band
Pin 9 all 0.00v apart from 50khz which is 12.18khz
Pin 10 all zero apart from 50khz at 13.18v and 60khz at 12.17v
Will run some more tomorrow as lots of figs to tecotd.
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Old 13th Mar 2023, 10:35 pm   #226
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Default Re: Help needed with - Racal Dana 9081

Hello Mark,

The latest set of readings seem to look more sensible. We now have enough to conclude that something is definitely not right about IC15. Pin 3 should be high under the conditions you are reporting, but it is low. Check in case pin 3 is shorting to an adjacent pin, but I think IC15 will need to be replaced.

The different voltages when the input pins are high can be explained by the way the various step lines are connected. There are diodes which, in some positions, will allow the switch to feed more than one line at a time. Lines fed via the diodes will be at a diode drop lower voltage than those fed directly from the switch. In some positions, the voltage will be two diode drops lower on one line.

Paula
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Old 13th Mar 2023, 11:34 pm   #227
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Default Re: Help needed with - Racal Dana 9081

Quote:
Checked IC15 pins as follows, certainly not as expected:-
Pin 1=0.00v no change of reading throughout each band & across each range.
Pin 2= 1236v , same state as above
Pin 3= 0.00v, same state as above

Pin 11= 12.17v no change of reading throughout each band & across each range
Pin 12= 10.10v same state above
Pin13 = 0.00v same state as above

Pin 8= 0.00v
Pin9= 0.00v
Pin 10 = 0.00v
All no change of reading throughout each band and across each range
Some of the input pins on IC15 should be changing state as the channel spacing switch is rotated.
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Old 14th Mar 2023, 8:32 am   #228
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Default Re: Help needed with - Racal Dana 9081

Hi Paula,Peter
Will check pins / tracks and if no shorts etc will change IC15, will need a few days to source one as cant see i ordered one in the batch of IC’s i sourced. Looked at the board and will also order a CD4030AE as don’t have one of those either in case needed, have all the others.
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Old 14th Mar 2023, 6:36 pm   #229
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Default Re: Help needed with - Racal Dana 9081

Hello Mark,

Looking over your measured results and comparing them with the switch arrangement on the circuit diagram, there are some inconsistencies in what you have observed.

The voltage on pin 9 of IC15 should be high for the 50kHz and 60kHz settings. You found that the output pin (pin 10) matched that, so you probably had a poor contact to pin 9 when you measured there.

The voltages on pin 2 of IC15 were as they should be for all positions except:

a) the 5kHz steps one which should be 0V Possibly there is a wire shorting that could be giving that incorrect result.
b) the 6.25KHz position should be 12V.
c) the 12.5kHz position should be 11.3V.

The final set of results relate to pin 12, where you measured 0V for all switch positions.

What you should have seen is:

0V: 5kHz, 10kHz, 6.25kHz, 15kHz

12V: 20kHz, 12.5kHz, 25kHz, 30kHz

11.3V: 50kHz, 60kHz.

I wonder if there is a wire disconnected between the step switch and terminal 25 on the logic board, or if there is some corrosion on the pins of IC15 preventing reliable contact.

Paula
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Old 14th Mar 2023, 7:52 pm   #230
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Default Re: Help needed with - Racal Dana 9081

Hi Paula
Your knowledge on this unit is amazing, will double check all the points you mention and confirm the results.
Thanks again for all your help with this.
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Old 14th Mar 2023, 9:59 pm   #231
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Default Re: Help needed with - Racal Dana 9081

Hi Paula
Results as follows:-
Pin 2 IC15
5khz is 10.12v
6.25khz is 10.13v
12.5khz is 12.36v

Pin 12 IC15
Figures (volts) band 1 left, band 5 right
5khz 9.77, 0.00, 10.79, 9.77, 1.10
10khz 10.13, 0.00, 11.24, 10.14, 1.10
6.25khz 9.76, 0.00, 11.24,10.14, 1.10
15khz 10.13, 0.00, 11.24,10.14,1.10
20khz 12.36,12.36, 12.36,12.36,12.36
12.5khz 10.09,0.00, 11.23,10.13,1.10
25khz 12.36,12.36,12.36,12.36,12.36
30khz 12.37,12.36,12.36,12.36,12.36

Pin 25 logic board has continuity from pin 25 to IC15 pins 7, 12 and 24. I will have to look at tracing the wire from the switch as looks bit more involved. Cant see any dodgey joints or tracks around ic 15. Hope the above is a better set.
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Old 14th Mar 2023, 11:14 pm   #232
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Default Re: Help needed with - Racal Dana 9081

If you check the switch logic for S4 (Channel switch) you should get the following table.
(Switch S4 1F)

Code:
      
              SZ     SY     SX
1   5         0      0       0
2   10        1      0       0
3   20        0      1       0
4   6.25      0      0       0
5   12.5      1      0       0
6   25        1      1       0
7   50        1      1       0
8   15        1      0       0
9   30        1      1       0
10  60        1      1       1
11  A	      0      0       0
12  B	      0      0       0
SZ = IC15 pin 2
SY = IC15 pin 12
SX = IC15 pin 9

You get nothing like this!

In the 5kHz position you should never get a voltage on IC15 pin 2!!!!

Are you sure the knob is fitted in the correct place on the shaft?!

Can you find this pattern by rotating the channel knob (ignoring the displayed values)

If not plot table for SZ, SY, SX on each channel switch position as above and look for stuck logic levels.

Also pretty sure that the spacing logic on IC15 is same for all bands

Please write logic levels as 1 or 0! writing the measured voltage makes it difficult to see what is happening. Below 3V = logic 0, above 8V logic 1 please. Anything between 3v and 8V is indeterminate in a 12V logic system.

So you have IC15 pin 12

Code:
5kHz     1, 0, 1, 1, 0
10kHz    1, 0, 1, 1, 0
20kHz    1, 1, 1, 1, 1
6.25kHz  1, 0, 1, 1, 0
12.5kHz  1, 0, 1, 1, 0
25kHz    1, 1, 1, 1, 1
50kHz 
15kHz    1, 0, 1, 1, 0
30kHz    1, 1, 1, 1, 1
60kHz
A
B
Why are you listing channel spacing out of sequence, and missing out some spacings?

It all makes it difficult to follow what is going on! Logic circuits are often just about recognising patterns....

Also when testing the channel spacing, make sure you are in SLOW tuning speed!!!
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Last edited by PETERg0rsq; 14th Mar 2023 at 11:43 pm.
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Old 15th Mar 2023, 9:11 am   #233
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Default Re: Help needed with - Racal Dana 9081

Hello Mark/Peter,

I don't want to rock the boat but we need to be careful that we don't throw away useful data in rounding voltages to 1s and 0s. We would never have found the cause of the end stop circuit problem had Mark only reported the band 1 feed to the ROM as a 1 or a 0. It is no hardship to me to convert from voltage levels to logic states, while still giving valuable information. In this case, there are some 9V levels, which are probably due to the resistors on the phase detector board, but I need to check the circuit to be sure.

The Sy levels for Range 2 appear to match your values, Peter. It does seem that the range switch makes a difference to the Sx, Sy and Sz levels. I thought the circuit shows the switch in position 1, but the Sy voltages on position 1 are different to those I had expected.

Mark,

Is IC15 really faulty or is the problem that there is /was a bad contact to the output pins, 3 and 10 when you tried measuring them?

Paula
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Old 15th Mar 2023, 8:04 pm   #234
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Default Re: Help needed with - Racal Dana 9081

Hi Peter /Paula

Just noticed the wire that connects to pin 17 of the logic board has become detached, i will refit it and then check pins 3 & 10 again. I had checked for shorts etc around IC15 but couldnt see anything out of the ordinary.
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Old 15th Mar 2023, 8:23 pm   #235
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Default Re: Help needed with - Racal Dana 9081

IC15 pin 2 is showing some voltage change when the channel spacing switch is forcing it to 1 so it would be worth checking the 10K pull-down resistor (R34).
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Old 15th Mar 2023, 9:37 pm   #236
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Hi Paula
Refitted the wire and re-ran the tests on pin 3 & 10 on IC15.
Pin 10 IC15
Band 1 = 12.14v across every channel spacing (5khz-60khz)

Band 2
5khz = 0.00
10khz = 0.00
20khz = 0.00
6.25khz = 0.00
12.5khz = 0.00
25khz = 0.00
50khz = 12.17
15khz = 0.00
30khz = 0.00
60khz = 12.17

Band 3
5khz = 0.00
10khz = 0.00
20khz = 0.00
6.25khz = 0.00
12.5khz = 0.00
50khz = 12.17
15khz. = 0.00
30khz = 0.00
60khz = 12.17

Band 4 = 12.18 across every channel spacing

Band 5
5khz = 0.00
10khz = 0.00
20khz = 0.00
6.25khz = 0.00
12.5khz = 0.00
25khz = 0.00
50khz = 12.18
15khz = 0.00
30khz = 0.00
60khz = 12.18
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Old 15th Mar 2023, 9:38 pm   #237
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Default Re: Help needed with - Racal Dana 9081

Pin 3 IC15
Get 0.00v on all bands and every channel spacing.
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Old 15th Mar 2023, 10:28 pm   #238
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Default Re: Help needed with - Racal Dana 9081

Hi PJL
I will check R36 as suggested and confirm result.
Thanks
Mark
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Old 15th Mar 2023, 11:07 pm   #239
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Hello Mark,

I think we can conclude that IC15 is faulty after all your tests.

I've had a much closer look at the switching arrangements and have seen that on bands 1 and 4 there is a path where 12V is applied to pin 9 of IC15 via a 100k resistor, by a rather convoluted path. You should measure 1V or so, rather than 12V via that path. PJL is right that you should check the resistors R34, R35 and R36 (R36 in particular), as an open circuit one, or a bad connection there will result in what you are seeing.

Paula
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Old 16th Mar 2023, 12:41 am   #240
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Default Re: Help needed with - Racal Dana 9081

Is Paula referring to R34, R35 and R36 on the Phase Detector and Divider Board or the same–numbered components on the Front Panel Circuit Diagram, Fig. 20?

I'll a little puzzled because R36 in Fig.20 is part of two resistors in parallel forming the 600 Ω input resistor across the "Ext A.M. Socket" SK98!

Chris Williams

PS!

There's four (possibly five!) different Maintainence Manuals known to be on the go for these two Models of Racal Signal Generator, none of the online ones posted are complete, and one hasn't been shared online at all!

So far I've identified:–

a) What appears to be a first issue, Racal ref. WOH7204 dated 1976, and there's no ALC circuit components shown on the Oscillator Circuit 19–0841 ;

b) A later issue dated 8–2–82 which has an appallingly bad scan from Mauritron missing at least thirty pages ;

c) What appears to be the latest edition dated 10–8–83 online, missing all the 9081 and 9082 diagrams Figs 1 to 22 ;

d) A "9082" (only) Maintainence Manual which appears to have been published in a different typeface, I have this on paper (which I've buried somewhere!) but there's no scanned copy of this ;

e) Possibly there exists an original Maintainence Manual for the 9081 only, but I've not seen anything like this on paper or PDF yet!
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Last edited by Chris55000; 16th Mar 2023 at 12:56 am.
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