Uher 4000 Report Monitor Amplifier Component Layout

[DMcMahon]

Hello All,

My first post to the forum. I am repairing a Uher 4000 Report Monitor for a friend. It has record and playback issues and I am fault finding the amplifier board but am having trouble correctly identifying the relevant components (not helped by eyesight not being as good as it used to be).

After much searching I found an Hungarian electrical schematic (circuit diagram) but have been unable to locate a component layout drawing (the various other 4000 models, some of which do have component layout drawings are not very similar).

So hoping someone can advise where I could source the relevant drawing please.

Thank you and regards,

David

[TIMTAPE]

What are the record and playback issues? With tape machines, they're not always due to the electronics.

[DMcMahon]

On Playback there is no sound, just occasionally get very short bursts of sound.
Tried several known good tapes all with same results. Heads have been thoroughly cleaned and DC voltage supplies checked OK, tape is making proper contact with the playback head.

On Record, get good record signal on the record level VU meter and hear good signal on the speaker (when Monitor switched to source) but when recorded tape played back, there is no recording heard (Monitor switched to Tape). Same bad results when recording to other tapes. The recorded tape from 4000 when tried on other R2Rs also gives no playback sound.

[orbanp1]

Hi David,

This site has several documentations, including the PCB layouts:
https://cryptomuseum.com/covert/rec/...port/index.htm

Regards, Peter

[DMcMahon]

Hi Peter,

Thank you but I have already visited that site (and many others) I will double check but am almost 100% certain that the 4000 Report Monitor schematic and component layout drawings are not there. The Service manual is there but unhelpfully does not contain these drawings.

Page 6 of the Service Manual does have a very poor quality (very difficult to read) sort of component location drawing, but it is very different from my 4000 board, I guess it is either a 4200 or 4400 Report Monitor board that the manual also covers.

Regards

David

[ms660]

Not sure if you've seen this manual, Uher 4000 Report Service Manual, you can download it from vintageshifi:

https://www.vintageshifi.com/repertoire-pdf/Uher.php

Lawrence.

[DMcMahon]

Hi Lawrence,

I have thank you, but the manual on this site (which does have schematic and component layout) is for the 4000 Report IC, which is similar but different. I do have the correct 4000 Report Monitor Service Manual, but this manual does not have the schematic or component layout.

I did find the correct 4000 Report Monitor schematic as 3 pages numbered pages 37-39 from a Uher Repairs Manuals CD that I purchased from eBay. This was in Hungarian so presumably there is an Hungarian Uher document that contains these 3 pages, which I assume must be a Service manual, whether it also contains the component layout drawing I do not know.

David

[barretter]

You can buy a Uher 4000 Report Monitor Circuit Diagram and Service Instructions leaflet which is an A2 folded sheet with circuit diagrams and parts placement diagrams from
sds-consult.de/UHER/
for 3.57 Euros + postage.

[DMcMahon]

Many thanks, I will check that out, it is very helpful.

David

[barretter]

Here are a couple of photos of the front and back of the leaflet to give you an idea of its contents.
The shop's URL doesn't seem to work properly so just type it into Google and it should open the site OK

[DMcMahon]

Looks excellent ! I have downloaded their price list, they do an extensive list of Uher parts and documentation etc. Have messaged them asking for total price figure to ship to UK.

[DMcMahon]

Got price from SDS of 11.97 Euros for tracked UK shipping of the the said documentation, so have placed order.

[DMcMahon]

I see that in the 4000/4200//4400 Report Monitor Service manual it does list the circuit diagrams as pages 40 - 44 but looks like most if not all of the downloadable Service manuals end at page 39.

[barretter]

As far as I recall the circuit diagrams are on large fold-out sheets which are not amenable to A4 scanning.

[DMcMahon]

Yes makes sense.

[DMcMahon]

Last night I did quite a bit (time wise) but no real progress yet. I was looking at the Playback amplifier (using oscilloscope and voltmeter to monitor relevant parts of the circuit) to diagnose why Playback does not work properly. Test methodology was to connect test equipment to relevant area, then power on the 4000 then press Play (with recorded tape loaded) or leave Play selected then power on. This gives a short burst of good sound (less than 2 seconds) then after that there is no more sound until the 4000 is powered down then re-powered after a few seconds then a second single sound burst is obtained etc etc.

It gives the impression that a component such as a capacitor or a transistor etc may be breaking down, but as of now, have not been able to locate the source of the problem. I am reasonably confident (and very hopeful) that with time will resolve it.

One very strange & interesting thing is that I can easily see on the scope, the short sound burst in the later stages of the Playback amp going to the loudspeaker, but cannot see the sound burst signal in the early stages of the amplifier, but as the signal is getting through to the output there is obviously a signal at the input side , just cannot see it so far.

I can see the sound burst signal where the Playback head wiring enters the board at Tantalum electrolytic input capacitors C1 & C2 but there appears to be no signal (as monitored on scope) at the output of these capacitors or their surrounding transistors during the sound burst, which to me technically does not make much sense.

Have done basic in circuit static (no power) checks of many of the capacitors measuring capacitance and measuring resistance across the capacitors to ensure no short circuits or low resistances, so far all looks good. In circuit checks are not ideal due to other series/parallel circuits that might affect the test readings but so far all looks OK, if any suspect readings I would remove the component for out of circuit measurements.

Do not want to remove components unless really necessary, as the PCB artwork is quite delicate and many of the components are quite delicate, lots of soldering/de-soldering could do more harm than good, do not want to make a bad situation worse. Do not have the right equipment to do more comprehensive capacitor measurements such as ESR and leakage current etc.

Another problem symptom I am seeing is that when the 4000 is switched on (this time with Play not selected), very often get a lot of activity on the recording level VU meter, the meter needle jumps all over the place (even with record level and volume at zero) and can go hard over (to the right), this can last for a couple of seconds, then the meter settles down, but very occasionally randomly for very short periods the meter starts jumping around again (same in Source or Tape monitor).

Once again to me this indicates a component is breaking down generating noise spikes or going into oscillation etc, I am fairly sure the root cause of this symptom will most likely be the same cause as the short sound bursts.

[Welsh Anorak]

The needle dancing when you switch on seems normal - my 4200 monitor does exactly that, though I don't know why.
One thing that springs to mind is the record-play switch. This can wear and do unexpected things. Just a thought.

[DMcMahon]

Hi Glyn,

Thanks for that, good to know that jumping meter needle may not be that abnormal on the 4000/4200, although it does not seem correct to me. Yes good input ref the Record/Play switch, I will check it out. I am also suspicious of the Source/Tape Monitor switch as have seen & heard playback sound on this 4000 when switched to Source (with no source input) surely it should not do this.

Tonight had another session and got identical results as last night but about 10 minutes ago, I have lost all Playback audio, no playback sound/signal at all at any time now, maybe whatever was causing the short sound burst symptom, has now died all together.

The record amplifier circuit is still live when I plug in a microphone and can set up the VU meter and hear plenty of volume from the loudspeaker but as before when I then do a recording, there is no sound on playback.

David

[julie_m]

It's a three-head machine, so there isn't really a "play/record" switch in the usual sense; just a monitor switch to select the signal being fed to the recording head (Source) or the signal coming from the playback head (Tape), and a switch operated by the "record" button which turns off the erase/bias oscillator and leaves the erase and record heads de-energised when not recording. The recording and playback amplifiers are completely separate, with no fancy rewiring of components to perform different duties in each mode.

If tapes recorded on your Uher play OK on another machine, then that suggests the fault is in the playback circuitry of the Uher.

Can you inject a signal at various points along the playback path and have it come through the speaker? This way, you should be able to isolate the fault to a particular stage (it must lie upstream of the last injection point that worked).

[DMcMahon]

Thank you Julie, I was thinking of getting my signal generator out of the attic (just have to find it) to do some signal injection tests. Yes understand about no Record/Playback switch.

The record amp also appears to have a fault (maybe there is a common fault affecting both amps) because when recordings done (all looks good/normal on the record level VU meter etc) those recordings when played back on other recorders also gives no recorded playback.

May not get a lot more done on the 4000 for a day or two as have many other things to do including having a quick look at my latest R2R acquisition a late 50's Grundig TK 36.