Uher 4400 Report Stereo IC Checkout
 

Brought this early 1970's 4 track, 4 speed, solid state, stereo, reel to reel a while back from a Forum member, one of the many variants of the Uher 4xxx Report family.

Its operational status was unknown but possibly thought to be a runner.

Internally it has a strong musty smell so have left it open for many weeks and the smell is slowly dissipating.

It came with a tatty black leather carrying case (no strap) but nothing else apart from an empty 4" tape spool.

Overall not in bad condition but a little tatty externally with some rusting on top panel and some flaking grey paint on underside panel. Internally looks clean and tidy.

First thing spotted when looked inside is that the fast wind drive belt is missing, after a good shake several small bits of gooey belt fell out which I assume are remnants of the fast wind belt.

Tried powering it up today using my Uher Z 124A power adaptor (borrowed from my 4000 Report Monitor) fitted in the battery compartment, but no life at all. Tried another adapter (Z 124) but still no good. Checked both adaptors are working of course.

So a disappointing start, next will connect external PSU into the D type to see if it will power up.

David

Re: Uher 4400 Report Stereo IC Checkout
 

DIN not D type of course

David

Re: Uher 4400 Report Stereo IC Checkout
 

Powered the 4400 from external PSU connected to the 6 pin Access (Accessories) DIN socket, pin 6 -ve and pin 3 +ve (ground/battery +ve).

Still no good but can see that when Play or Fast Wind is selected the PSU voltage drops down to 1 volt and the current goes up to 350mA (not abnormal current when working normally). So something is badly loading the PSU supply.

Plan to disconnect some of the output wires at the little power supply board to see if the board has a problem or whether something external to the board is the culprit. It looks like the board will be a nightmare to get to properly, I can see that it has previously had some soldering work done on it.

David

Re: Uher 4400 Report Stereo IC Checkout
 

Looking at the documentation this morning can now see that the little board I thought yesterday was the power supply board is not, which is good because I now realise that the power supply board is under the top panel and the underside is accessible by removing the battery box, so will be much easier to view/access.

Should have remembered this from my previous work on 4000 Report Monitor which has similar power supply board.

David

Re: Uher 4400 Report Stereo IC Checkout
 

Found capacitor C404 on the input to the power supply board is a dead short so shorting any battery/external power supply input down to ground. The capacitor is 2,200uF 6V (shown as 8V on the schematic).

Another example of Uher using capacitors with voltage rating basically the same as the actual working voltage.

The black capacitor is C403 which should be another 2,200uF/8V but is a more modern 470uF/25V so someone has previously replaced C403 with incorrect value. The 470uF measures around 620uF with good ESR, but I will replace it with one of correct value. This is for the 5.9V supply out to the Playback and Record amplifier circuitry.

The third electrolytic is C402 1,000uF/6V (schematic shows it as 12V) which is another 5.9V supply out to the output amplifiers volume controls, this measures around 1,820uF with good ESR, will replace this also. Looking through my spare capacitors I only have one at 1,000uF which measures OK capacitance wise but has high ESR at 36 Ohms.

The green enamel resistor is R404 it should be 5.6 Ohms 0.5W but the green resistor is 3.9 Ohms so the original must have been replaced.

David

Re: Uher 4400 Report Stereo IC Checkout
 

Replaced C403 and C404 with new 2,200uF 16V, replaced C402 with NOS 1,000uF 10V and replaced the 3.9 Ohm resistor R404 with a 15 Ohm paralleled with a 10 Ohm to get the resistance closer to correct value of 5.6 Ohms.

Now when Start key pressed it powers up OK with the 5 DC rails out of the power supply board all good. Battery/power strength indicator works when Rec Level 2 control pulled out and illumination works when Rec Level 1 pulled out.

Motors runs OK and speeds up when fast wind/rewind is selected, not yet found a replacement fast wind belt to be able to test this aspect further.

No sign of the the Supply reel table driving when Start is selected so that is next to check out.

David

Re: Uher 4400 Report Stereo IC Checkout
 

Looking more closely now realise that the Supply reel table drive is via the same friction wheel as the drive for the fast forward drive, so both Play and Fast Forward are both driven by the same friction wheel which in turn is driven by the missing belt, so the missing belt is not just fast wind as I previously identified it.

David

Re: Uher 4400 Report Stereo IC Checkout
 

Supply Reel Table in Posts 6 and 7 should have read Take Up Reel Table.

David

Re: Uher 4400 Report Stereo IC Checkout
 

Good news, David! It looks like you've diagnosed and repaired properly, so let's hope the new belt means you can test playback.

Re: Uher 4400 Report Stereo IC Checkout
 

Missing drive belt replaced and heads/tape path cleaned. Did some general cleaning including removing front panel parts, internally still finding tiny bits of gooey drive belt which makes a right mess initially when cleaning.

Loaded a 5" tape and tape transport all works OK, all 4 speeds work fine, fast wind performance somewhat mediocre, but typical from my experience for the 4xxx Report series.

Playback sounds good, next need to check recording.

While repairing the power supply board noticed on the output board a small orange 100uF/6V electrolytic has some brown staining on it, think it might just be solder flux because the 2 black ground wires soldered next to it has large blob of solder that is right next to the staining. Later will check out the electrolytics on the sound output board for good measure.

David

Re: Uher 4400 Report Stereo IC Checkout
 

Checked recording using 2 microphones (Uher & Grundig). Note that the live on Grundig mics is pin 1 at the DIN plug and on Uher it is pin 2, so on this particular Grundig mic (GDM18Hi) I have previously wired the live to pin 2 for Uher testing.

Left channel records and playsback well.

The right channel microphone (Grundig) shows a good record signal on the right channel Record level VU meter but because there is only a single internal speaker, on the right channel you cannot hear the recorded signal on Playback without either connecting an external speaker/headphones to the right channel or connect the right line output to an external amp (or of course play the tape back on another stereo recorder with 2 speakers).

Very occasionally during recording the sound would go distorted or disappear (while monitoring on the internal speaker), also on playback of a good recording the same occasionally occurs. From various diagnostic tests it looks like the issue is due to the Track Select push button switches.

By removing various bits tried to use contact cleaner on the track switches but impossible to see/access from the front of the switches (with front panel parts removed)
may be able to get some contact cleaner in from the rear of the swithes but looks very difficult.

Then got side tracked to fix loose double VU meter assembly, there was some brown foam that the rear of the VU meter should push up against but the foam has gone hard and turning to dust, so replaced with new.

After spraying some contact cleaner toward the rear of the track push buttons (not sure if any actually got inside the switches) reassembled to retest recording/playback but now the speed change linkage is jamming.

David

Re: Uher 4400 Report Stereo IC Checkout
 

To clarify the use of headphones on this unit, it does not have any actual headphones socket. To use headphones you would either have to make an adapter or wire the headphones cable direct to the left and right 2 pin DIN external speaker connector sockets.

David

Re: Uher 4400 Report Stereo IC Checkout
 

Fixed the jammed speed change linkage arm, a U shaped metal bracket that the arm goes through to operate the equalisation slider switch on the Equalisation board was slightly twisted and fouling the arm.

When I previously stripped the front panel parts to try and spray contact cleaner into the front of the track select push button switches, I loosened a screw that I thought might retain the push button switch assembly but found that the screw secured the bracket and upon retightening it must have caused the bracket position to twist a little.

Re: Uher 4400 Report Stereo IC Checkout
 

Connected an external speaker to the right channel 2 pin DIN socket. Now when testing right channel recording can monitor the record signal through the speaker but zero sound on the right channel on playback.

Left channel still recording and playing back but still some intermittent operation, still looks due to the Track push button switches, had another go at spraying contact cleaner at the rear of the switches.

Also cleaned the left and right Play/Record switches but no change to either of the fault symptoms above.

The Uher microphone model M516 has 2 switches, a 2 way slide switch labelled S & M and a momentary push to make switch.

The slide switch is for selecting either Speech (S) or Music (M) recording profile.

The press to make switch is for remotely controlling Pause operation when tape is playing/recording. There is a strange problem with the remote pause operation.

With Play and Pause keys pushed down, the remote pause switch energises the remote pause relay/solenoid and the external power supply (that is powering the unit) voltage and current are good. But when the Pause key is deselected and the Remote Pause switch is pressed the solenoid does not energise and the power supply voltage drops off and current goes up, as if being heavily loaded.

David

Re: Uher 4400 Report Stereo IC Checkout
 

Started investigating the remote pause issue and the situation rapidly deteriated, now when unit is powered, the voltage drops off and current goes failry high, something is shorting/breaking down by the looks of it.

Frst will check out capacitors C84 (1uF 35V) and C62 (100uF 3V) which are across the 2 coils of the remote pause relay (relay A) think will need to remove the speaker to access the relay and capacitors.

Cannot see how they can be causing the current problem because their +ve side wil be effectlively floating when the Uher microphone remote pause switch is not pressed, but because the problem was first seen when the microphone switch was operated wonder if there is something wrong there. The service manual desribes the relay circiut as current limit which I do not fully understand.

David

Re: Uher 4400 Report Stereo IC Checkout
 

If relay A's contact doesn't break, relay A will try to pass at least half an Amp because the high power coil won't be disconnected, the high power coil should only operate for a fraction of a second, after which it should be disconnected by the relay contacts breaking, that then leaves the low power coil in circuit to provide the holding force.

Lawrence.

Re: Uher 4400 Report Stereo IC Checkout
 

Thank you Lawrence, fully understand now.

David

Re: Uher 4400 Report Stereo IC Checkout
 

No problem, by the way C62 losing part or all of its value might also result in excessive
current through the solenoids high power coil as its charge powers the high power coil for the last part of the armature travel after the contacts break.

Lawrence.

Re: Uher 4400 Report Stereo IC Checkout
 

Removed relay A and its 2 capacitors, then unit powered up OK, reconnected the relay and the power supply current limited as if too much load, did this sequence several times, sometimes it would power up OK other times it would not.

I think it is just a co-incidecnce that sometimes when the relay is connected that the problem occurs and that root cause is some sort of intermittent too high load issue.
With the microphone not fitted/remote pause switch made then there is no return path for the relay circuit/capacitors as they are effectively floating/not connected.

Measured the 2 capacitors they measured basically OK other than the 1uF read high at 3.3uF

I believe the root cause of the remote switch operation problem is that the power supply is just current limiting as it cannot not supply high enough current. The power supply is only a nominal 500mA with 150mA upwards being required for running the motor.

With the relay out of the machine (connected) it energises fine when remote pause is switched (there being no mechanical load on the armature plate) but when mounted in the machine it does not work, it tries to but the relay cannot energise as the voltage drops off and current increases but not enough to fully energise the relay.

I can see why, when Start is pressed (has to be pressed to get machine on) a metal sprung loaded lever moves down onto the relay armature plate, to move this lever up when remote pause is selected requires some force to overcome the inertia and because the power supply cannot supply high enough current to initially energise the relay (> 500mA as explained previously by Lawrence) the relay cannot move the armature plate so never actually switches its contact to disconnect the 11 Ohm relay coil to put it into the holding state.

Will replace both capacitors because the 1uF measures 3.3uF (which is probably fine operationally) and from Laurence's input that if too low value could cause issue. Will replace the 100uF 3 volt Tantalum because it sees around 6V albeit for very short time period.

Will try another power supply to make sure of the current limiting prognosis.

David

Re: Uher 4400 Report Stereo IC Checkout
 

Replaced radial electrolytic C84 1uF 100V (35V on schematic) with new radial 1uF 63V and replaced Tantalum C62 100uF 3V with new radial electrolytic 100uF 16V.

With relay A hanging out of machine tested the remote pause operation from the Uher mic, relay working fine as before.

While doing this noticed some tape that holds down the battery box wires at one end of the battery box was coming off so pulled it off and discovered the wires underneath were damaged with overheated cable insulation and all the wires stuck together from heat damage, with at least 3 down to bare metal, one of the wires crumbed apart when I disturbed it.

No obvious burning smells around the wires so I think this is old damage not recent.

Hard to imagine what could have caused this. Two of the wires that were down to bare metal connect to the 2 switches on the underside of the battery box, one must be K5 but cannot see a second one on the schematic for the battery box. I think the switches are supposed to isolate the batteries in the battery box when using external power from power supply/external power adaptor/accumulator batteries but not very clear at the moment.

So once I renew the wires I need to physically and electrically check the operation of the battery box switches.

David