{"id":1876,"date":"2024-05-18T22:11:09","date_gmt":"2024-05-18T22:11:09","guid":{"rendered":"https:\/\/storycase.co.uk\/radio\/?p=1876"},"modified":"2024-08-14T22:15:15","modified_gmt":"2024-08-14T22:15:15","slug":"uher-4000-report-s-portable-tape-recorder","status":"publish","type":"post","link":"https:\/\/storycase.co.uk\/radio\/tape-recorder\/uher-4000-report-s-portable-tape-recorder\/","title":{"rendered":"Uher 4000 Report S Portable Tape Recorder"},"content":{"rendered":"

Rescued from the scrap heap this Uher 4000 Report – S portable reel to reel tape recorder was manufactured between 1963 and 1965, superseding the original Uher Report 4000 introduced in 1961.<\/p>\n

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Uher 4000 S Report before restoration<\/p><\/div>\n

The 4000 S uses a 12 transistor design incorporating motor speed control enabling stable recording at four speed settings. Battery operation via 5 D cells was essential to meet its target market – the mobile news reporter. A million were made over its 40 year production. This S model is a two track mono recorder despite having an S suffix that can be confused with its stereo sibling.<\/p>\n

With a European heritage, the Uher is fitted with an array of DIN sockets for external devices ranging from a dynamic microphone, via the front panel 3 pin DIN, or radio and phono sources from a 5 pin DIN socket on the right hand side. Along side there\u2019s a 2 pin DIN connection allowing an additional speaker or headphone to monitor recording or playback. Unusually the internal speaker still operates when plugging in an external speaker. Finally a third side mounted 6 pin DIN socket supports an external 7.5v DC power source plus remote control. This socket isolates the battery to prevent reverse charging the dry cells. Internal power options support either 5 D batteries or a 6v rechargeable accumulator.<\/p>\n

Uher\u2019s compact design accommodates up to 5 inch reels allowing 1h recording on standard play tape an 3\u00be IPS. But the Uher could also operate at half and quarter speeds to provide up to 4h recording at 15\/16 IPS albeit with lower quality suitable only for speech. With a top speed of 7\u00bd IPS the 4000 S captures near high fidelity monaural recordings in conjunction with an external amplifier for playback.<\/p>\n

The 1W internal amplifier and speaker are sufficient for voice playback but suffers from some distortion on music likely due to low gain push-pull transformer coupled design. However, Uher\u2019s competence in their design circuitry is evident with negative feedback being used to lower distortion in each audio amplifier stage.<\/p>\n

Restoration and reapir<\/h2>\n

After removing 50 years plus of grime from the case and front panel the 4000 showed remarkable resilience for its age – see the before restoration image at the top. Superficially cosmetic damage was limited to a few knocks and peeling paint on the base. Its leather case was missing and likely protected the machine through most of the years. Missing too were its dynamic microphone and external power supply.<\/p>\n

After removing the base plate via the thumbscrew an initial ohms check across the battery connection showed no continuity with any control engaged. It\u2019s not immediately obvious what switches the Report 4000 S on. There\u2019s no On\/Off and the piano keys did not start the motor. Closer inspection found engaging the four speed control push lever registered a few tens of ohms on the multimeter across the battery contacts. But with 5 D cells inserted there was no sound or motor noise.<\/p>\n

Removing the tan card reveals the main circuit boards and a chance to trace where the battery connections lead to. Fortunately Uher service manuals are freely available, see end of post for links, so I could identify the main paths.<\/p>\n

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Uher 4000S internal circuit boards<\/p><\/div>\n

A pair of contacts were visible below the main flywheel which I cleaned using a thin strip of card soaked in switch cleaner. It\u2019s best to avoid squirting lubricating switch cleaner inside the mechanism to prevent accidentally coating the belt and rubber friction surfaces in oil.<\/p>\n

By inserting the card strip between the contacts and operating the keyboard switches it was possible to remove the oxide and lower resistance. The reading reduced from over 15 ohms to less than 1 ohm. Reinserting the batteries, the Uher jumped into life.<\/p>\n

Fault finding<\/h2>\n

The moment was short lived, when I turned the machine the right way up it promptly stopped working. Although no obvious corrosion the battery contacts must also have poor conductivity – it only takes one in the series of 5 to fail. After a thorough clean of all contacts using a fibreglass abrasive brush, along with re shaping the spring ends for a better fit, the Uher\u2019s motor worked again when turned upright.<\/p>\n

I had no 5 inch tape and the 4000 came with just an empty reel so I pulled a 3\u201d tape from a Benkson Thunderbirds tape recorder (see Thunderbirds Taperecorder<\/a>). The tape played, although just a buzzing tone could be heard. I\u2019d no idea what was recorded on the 3\u201d tape so tried finding a signal source to make a new recording – hoping the aging Uher would still record.<\/p>\n

My workshop Beomaster 3300 uses DIN connectors so I borrowed a DIN to 3.5mm jack lead and connected a portable CD player. To my surprise when pressing start, pause and record keys faint music played from the Uher\u2019s speaker. Adjusting the recording level and volume improved the sound level as the recording meter needle showed. With level set, I tried recording a few seconds of jazz. And on playback the jazz music could be heard although rather distorted to my ears.<\/p>\n

The schematic shows the same preamplifier transistors TR1 to TR4 being used for recording and playback. So I rigged up a sine wave source to replace the CD player and looked at the waveform across the preamplifier stages in record mode. There was obvious 2nd harmonic distortion with an uneven upper and lower waveform. I suspected the numbers electrolytic capacitors used throughout the preamp. But the voltage readings helpfully listed in the service manual all seemed normal. I tried a new 100uF capacitor across the various bypass caps to check if any had gone low value and hence reduced stage gain causing the distortion. No luck. There was little or no difference.<\/p>\n

I followed the sine wave signal through to the audio output stage and again there was obvious asymmetry that could account for the poor music quality. But why? I measured the battery voltage and found instead of 7.5v there was only around 5.5v at the main amplifier. This seemed odd so I checked the batteries. Doh – they were flat – the motor must consume some power and the cells I\u2019d pulled from my spare box were old. Normally I\u2019d rig up my bench supply to avoid the need for batteries but the Uher had no easy way to clip on the positive power source. The + battery terminal was recessed and no wire was not accessible.<\/p>\n

Looking at the circuit diagram I could see the 6 pin DIN socket can provide power so I hunted for a suitable plug. It\u2019s been years since I played around with anything other than standard 5 and 2 pin DIN plugs. Luckily I found a 6 pin plug with signal leads and wired up the bench supply. Given there are several high value electrolytics in the Uher 4000\u2019s supply line it\u2019s important to use a regulated DC supply too higher voltage that can damage the aging capacitors.<\/p>\n

With the bench supply the audio signal magically became a sine wave again with no obvious uneven waveform. I tried the CD source and recorded a few more seconds of jazz. It sounded better via the record monitor but playback was still patchy.<\/p>\n

It was time to check the tape heads, a job I should have done earlier. These are accessed by removing the two small screws holding the cover. I used some ear buds soaked in isopropyl alcohol to remove years of brown oxide and residue. I did the same with the pinch roller to restore it to black from muddy brown and removed years of dust from around the heads. Clearly the reporters had been more intent on their story than maintaining their equipment!<\/p>\n

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Uher 4000S tape heads<\/p><\/div>\n

Notice the felt pad that pushes the tape against the central record \/ playback head has disintegrated – compare this with the pad used on the erase head that’s much thicker. I cut a rectangle from a similar thickness self adhesive felt pad to fit as shown below. \u00a0The new pad avoids damaging the tape and head.<\/p>\n

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Replacement felt pad<\/p><\/div>\n

Microphone input<\/h2>\n

After cleaning heads and pinch roller and replacing the felt pad I made a new recording where playback sounded clearer. I really needed to find a microphone to hear what the Uher could do with voice – its main forte. I tried a Beomic 2000 that’s fitted with a 3 pin DIN that plugs straight into the front panel. However, the Beomic failed to record any sound.<\/p>\n

Next I found a True Sound dynamic mic with an XLR connector and a lead with a 1\/4 jack plug – not suitable for the Uher. So I made a DIN to jack lead to avoid changing the mic’s existing lead and plugged them in. Feedback from the internal speaker confirmed the mic input was okay and a voice recording test sounded good. \u00a0An original Uher \/ AKG dynamic microphone would complement this recorder, so I will keep a lookout.<\/p>\n

After restoration<\/h2>\n

Gallery showing the Uher Report after cleaning and restoration.<\/p>\n

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Uher 4000S before and after<\/p><\/div>\n\n\t\t