Faulty Motorola 2001D/HS Service Monitor

[gandalfg8]

I've got a 2001D/HS Service Monitor, excellent condition outside, as new inside, and just about as dead as can be.
Power light works, oven light comes on after a few minutes as expected, then...nothing.
I'm assuming a power supply fault but need the schematic to check it out, does anybody know please where I can find one?
I've also noticed there's an empty slot in the card frame, board A13, but not sure if this has been removed or if it's an option that's not been fitted.
Any information would be very much appreciated.
Regards, Nigel.

[xmo]

The service manual for the 2001D is no longer available from Motorola. Even when they were available they were very spendy.

You can get a scanned pdf version on ebay, for example item number 250320744429.

I have no idea how good those scans are - maybe someone who bought one will chime in.

[DJP126]

I've got a 2001D/HS Service Monitor, excellent condition outside, as new inside, and just about as dead as can be.
Power light works, oven light comes on after a few minutes as expected, then...nothing.
I'm assuming a power supply fault but need the schematic to check it out, does anybody know please where I can find one?
I've also noticed there's an empty slot in the card frame, board A13, but not sure if this has been removed or if it's an option that's not been fitted.
Any information would be very much appreciated.
Regards, Nigel.

The A12 & A13 slots are for options. You should have a jumper board in the A12 slot (for audio routing). The A5 board (in the LVPS) has about 8 test points at the top of the board. These are your LVPS outputs. With the analyzer unplugged, check these to chassis ground with an ohm meter. TP1 or TP8 should show a direct short, the others should be fairly high except for one point will be around 45 ohms (unfortunately I don't remember which). If these measure O.K., the problem is USUALLY in the front panel OR the HVPS.

[bernie]

My two bits worth:
The power, and oven lamps as well as the oven circuit is powered by the battery charger power supply on the A-3 board.
The main switching supply is not running.
I would test the diodes on the A-5 board. I find that these diodes often short, causing no operation of the switching supply.
(CR 3-10, 48-80348B23 100V Shottkey diode.) This is a fast recovery diode, do not use a garden variety 1N7000 series.

While you have it apart you might want to inspect a few other potential problems. Be very sure to un plug the unit and allow the caps to discharge before disturbing anything.
Look at the large filter caps on the A-6, I have seen these fall off the board due to rough handling.
Battery charger board, A-3 be sure the transformer mounting screws are tight.

[gandalfg8]

Hi All

Many thanks for your replies and apologies for the slow response but I've been busy with other things and not checked back until now.

I should now have a pdf copy of the manual on the way but will check out the suggestions here whilst I'm waiting and will update soon.

regards

Nigel

[gandalfg8]

Well whaddya know......

one of the Shottkey diodes on A5 is short circuit:-)

And a rather messy replacement of one of the radial caps on A5 with an axial type laid across other components is at least possible evidence of problems being chased in this area before.

[bernie]

My two bits worth:
This is a common failure.
I would replace whatever caps are required to return the board to original condition.
Unless there is a problem with damaged traces, or some other reason.

I use caps from the parts store, never originals, nothing magic about them.

[gandalfg8]

Hi All

I finally got round to replacing the faulty diode, crossed my fingers, buried my head in a bucket of sand, switched on........
and have had a working 2001D for the last few hours:-)
Given that I was told this hadn't worked for two or three years it was a bit of a nail biting experience waiting to see what else might be wrong and a huge relief to find that everything seemed to be working, I'll worry about calibration later.

Many thanks to Dave and Bernie for your advice and assistance, it's been much appreciated, and I'm hoping you might be able to assist me once again.

When I was first removing the plug in modules from the power supply section two pieces of plastic fell out of the unit, presumably from the PSU area but I'm not sure.
The two pieces are identical, even have the same part number written on them, 94990-14-P24142A001, and are 5 1/2 x 3 inches.
The plastic looks like it has a weave inside it, a bit like fibreglass, so I assume they're intended to be insulators and perhaps for high voltage.
Held such that one long edge is at the bottom there's two 1/4 inch holes at the top, about 1/2 inch in from the sides, and a 3 1/4 x 7/16 slot cut centrally just above the bottom edge.
Neither piece has any marks that might indicate it's been fastened or attached to anything else and, however much I try, I can't see anywhere these might have come from, any suggestions?

regards

Nigel

[bernie]

Nigel:
That insulator goes between the control board (A4) and the charger board (A3).
Line voltage vs logic voltage is not a pretty sight, there is line voltage in the transformer on the A3, I have had to repair units where the transformer came loose and eventually contacted the control board.

There are many adjustments that can be done with little more than a VOM. You should degauss before attempting any CRT alignment. (A2). A big coil like TV repair men use.

I am very happy that you got it going. Just be very careful not to transmit into the antenna port. In fact NEVER monitor with an outside antenna with the attenuator at 0, because a near by strong signal will burn out the mixer in the receiver.

Ditto for the duplex port.

[gandalfg8]

Hi Bernie

Thanks for the information re the insulators.

I'm still waiting to get hold of a copy of the 2001D service manual, I do now have the manual for the 2001A but, mechanically at least, that seems to be a lot different so I can't confirm the insulator part number.
From the number I gave is that definitely the correct part?
I can slot one, or both, in between A3 and A4 as you suggest but they're about 3/4 inch narrower than the boards and just float about in the gap.
They will act as separators but do seem a bit hit and miss.
The cutouts in the insulator don't line up with anything on the boards either so they do look as though they were made for something else, was it perhaps a late afterthought to use them here?

Thanks too for the advice, again lack of manual means I won't be tweaking anything for now that isn't on the front panel, but I'll keep it in mind, especially the monitor ports and attenuator warning. I'll try to remember to set the attenuator to max when I switch off.

At the moment I'm just monitoring a local VHF radio station, a sort of background comfort factor while I can hear it's still working:-), but will check it out more thoroughly later.

Another mechanical question.......
The four small countersunk screws that fasten the A6 module to the chassis plus the two screws that hold the A3 module to the captive cage nuts are missing, although the PSU cover plate with its two screws is still fitted.
By lucky trial and error I've identified the A6 screws as 4-40 UNC but not sure on those for the A3 module.
If possible could you confirm those screw sizes for me please, I'm sure I can get the correct screws over here but I'm not familiar enough with American thread sizes to know what I'm looking for.

BTW
I've discovered what is either a manufacturing defect on this particular unit or may be a general mechanical design flaw on the 2001D.
If general it may be common knowledge anyway, so apologies if I'm telling you what you already know, but of the notches cut in the rear edge of the motherboard to provide clearance for the bottom cover fixing screws the central notch is in the wrong place.
It's offset from the screw, perhaps by half an inch, so the supplied screw does bear on the edge of the board and can be seen to distort the back panel slightly as tightened.
It really needs a shorter screw, or a new notch to be filed in the board to avoid the need for a different fixing, but I've just added a couple of extra spacing washers for now.

regards

Nigel

[Wowbagger]

I am very happy that you got it going. Just be very careful not to transmit into the antenna port. In fact NEVER monitor with an outside antenna with the attenuator at 0, because a near by strong signal will burn out the mixer in the receiver.

Ditto for the duplex port.

Another good piece of advice: don't use an uninsulated antenna. I've seen some antennas that are little more than a section of wire soldered into a BNC connector - throw those away! You can get an ESD event that will blow out the front end. It is VERY difficult to make an ESD protection circuit that won't load the port and change the impedance away from 50+0j ohms over 100kHz-1GHz.

Always use an antenna with the active elements insulated from the world, and ideally always touch the case of the instrument before connecting or disconnecting anything.

[DJP126]

Hi Bernie

Thanks for the information re the insulators.

I'm still waiting to get hold of a copy of the 2001D service manual, I do now have the manual for the 2001A but, mechanically at least, that seems to be a lot different so I can't confirm the insulator part number.
From the number I gave is that definitely the correct part?
I can slot one, or both, in between A3 and A4 as you suggest but they're about 3/4 inch narrower than the boards and just float about in the gap.
They will act as separators but do seem a bit hit and miss.
The cutouts in the insulator don't line up with anything on the boards either so they do look as though they were made for something else, was it perhaps a late afterthought to use them here?

Thanks too for the advice, again lack of manual means I won't be tweaking anything for now that isn't on the front panel, but I'll keep it in mind, especially the monitor ports and attenuator warning. I'll try to remember to set the attenuator to max when I switch off.

At the moment I'm just monitoring a local VHF radio station, a sort of background comfort factor while I can hear it's still working:-), but will check it out more thoroughly later.

Another mechanical question.......
The four small countersunk screws that fasten the A6 module to the chassis plus the two screws that hold the A3 module to the captive cage nuts are missing, although the PSU cover plate with its two screws is still fitted.
By lucky trial and error I've identified the A6 screws as 4-40 UNC but not sure on those for the A3 module.
If possible could you confirm those screw sizes for me please, I'm sure I can get the correct screws over here but I'm not familiar enough with American thread sizes to know what I'm looking for.

BTW
I've discovered what is either a manufacturing defect on this particular unit or may be a general mechanical design flaw on the 2001D.
If general it may be common knowledge anyway, so apologies if I'm telling you what you already know, but of the notches cut in the rear edge of the motherboard to provide clearance for the bottom cover fixing screws the central notch is in the wrong place.
It's offset from the screw, perhaps by half an inch, so the supplied screw does bear on the edge of the board and can be seen to distort the back panel slightly as tightened.
It really needs a shorter screw, or a new notch to be filed in the board to avoid the need for a different fixing, but I've just added a couple of extra spacing washers for now.

regards

Nigel

Almost all of the screws are 4-40, 6-32 or 8-32. The insulators were "added" after quite a few years of manufacture and originally came from some other piece of equipment. That is why they don't fit the analyzer. Instead of throwing the now useless insulator out and design a new one for the R2000 series, Motorola just transferred the part. They also used the "cardboard" insulators as separaters but you don't see those too often.

[gandalfg8]

Thanks Dave

I guessed it was something like that with the insulators but just wanted to check in case I was missing something.

regards

Nigel