Betamax PALsite : Technical Centre

Technical

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Idler Assembly

Fault and repair guide

No reel rotation

This is a very common problem which can have several causes. The first thing which fails is usually the reel idler assembly. Replacement units are readily available and can be fitted easily after removal of the cassette carriage. Before replacement check for a broken reel motor belt. This is a small belt which transfers drive to the idler. Finally, the last thing to suspect is the reel motor. Sanyo produced a modification to improve drive to this motor. This involved decreasing the value of the in-series resistor in the motor power supply (replacing a 3.3Ω with a 2.2Ω). However, it is not uncommon for the motor itself to fail in which case it needs to be replaced.

No tuner input

This is usually caused by failure of the RF combiner / splitter unit. Unfortunately it is not easy to repair this unit.

Timer and/or standby LED fail to illuminate

This is caused by dry joints where the LED are soldered onto the front PCB. In order to gain access to the PCB you'll need to remove the front panel and the servo board on the LHS of the deck.

Loss of servo lock in record

Recordings can suffer from a loss of drum lock which produces a picture roll and usually occurs between sudden bright/dark transitions. It is caused by problems with the sync separator in the servo circuits, usually due to dried out electrolytic capacitors.

System Control Bug

The machine had a strange bug in the system control software. Whenever an error occurred with the tape transport the VCR would lace up and shutdown. This is exactly the opposite of what you would expect and made sure that it was not possible to remove the cassette without damaging the tape. This 'feature' was not present in the later VTC-5150 model.

AM / PM clock modification

12 Hour Clock Display Mod

On the clock PCB there is a position for 12H or 24H clock. Usually they are 24H, but fit a 1N4148 diode in this position (note polarity as per PCB marking) and you get 12H clock with AM/PM illuminated in the display.

Further Information

For further information on general servicing on this model, take a look at Colin McCormick's excellent guide on How to service a Sanyo Beta.

Colin is also able to supply a service kit for this model.

Quick fault guide

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Fault	Solution
No function or power LED's working. 9 Volt supply dead on SY2	Print broken next to pin 19 (S3004) on servo board SY1. Jumper wire fitted to bridge gap.
Fluttering noise in playback	VR10 adjusted till stable reproduction on SV-1 Servo board. Some electrolytic capacitors on that board may need to be replaced.
Clock resets to 88:88 (and blinks) when switching the VCR to ON position	Replace the C5207 16v 100uF capacitor located on the large PSU board.
Machine won't rewind/fast forward and cuts out after a few seconds	Replace the reel idler belts and tires.
Tape will not lace up fully then stops and unlaces	Remove idler and base plate give a good clean remove both reels clean main shafts light oil plus bearings
Unstable color with horizontal lines on playback	Replace 2200uF 35V capacitor in the small power supply board.
Bad picture on video output terminal, good picture on RF output	Replace capacitor C1080 on the VD-1 board. Also applies for the VTC 5150 and VTC 5550.
The tape wil load the tape but not unload. Tape jam follows	There is not enough motor torque to pull the tape back to the cassette. The motor needs lubricating. Perform a mechanical maintenance of the right take up and surrounding parts. Add a small drop of precision oil to the bearing area of the main reel motor. Access the bottom part of the machine, locate the motor. Unscrew its bottom "cap". You will see the bottom bearing. It is very important to add 1-2 drops of precision oil here and a to be on a safe side, also a little bit of precision, thin grease (G 1/3 by Orelube for example). This procedure will save most motors.
Detailed YouTube video on servicing Sanyo video recorders	https://www.youtube.com/watch?v=VHT3QJ-r2w0
black zig zag lines on screen when playing a tape. Also some bad recordings	The head control box at the top left hand of the beta. This has a earth clip with black wire that hold it into place and earth the box. Your box will most likely be rusty or dull grey. The earth has bad connection. Remove the box and very carefully remove cover that sits at the back of the beta. Then solder a wire to the PCB at the terminals that connect PCB to the outside case. Now bring this wire outside box, and refit back cover. Refit box and solder the new wire to the black one that you removed from clamp. now you are done. it has fixed 6 of these for me and friends!!
Take-up not working	Check reel motor for dead spot or IC3006.
Mains fuse blown	Check regulator IC5101 and mains filter capacitor 0.0047μF. Also check fuse is anti-surge type.
Poor capstan servo lock on own recordings	Add 390 Ohm resistor across R4515.
Intermittently stopping in record or playback	If this is not due to faulty reel motor/take-up, then check output of reel sensor optocoupler for 6 volt peak to peak. If it's significantly lower then clean or replace the optocoupler.
Tape looping during unlacing	If the reel drive is ok, then change R3049 to a value of 1R0.
Vertical red and green stripes on the pictures	Replace VC1 trimmer capacitor on the video board with one of a 50pf value.
Intermittently pauses itself when playing cassette, counter works fine	symptoms continued... and plays fine with no cassette but counter intermittently not counting. Solution: C5204 on PSU needs checking. Found one example to be low in value, ESR high at 12Ohms and leaking electrolyte on the board.
Very bad tuner input with distorted picture and hum in the sound (VTC 5550)	"ALWAYS +33V" (tuning voltage) rail low at 26V in the power supply. Confirmed fault by swapping the power supply unit with one from a VTC 5000. Will update the post once the faulty component(s) has/have been found and the original power supply is repaired successfully.
Tuner supply voltage fault update (see above)	C5203 (100uF 100V) was the culprit. It had physically leaked and upon desoldering it the positive lead fell off due to it being corroded. Replacing that single capacitor fixed the problem. This applies to both the VTC 5000 and 5550 (Middle Eastern PAL/SECAM version).
On play there is no image but sound	On the main board, the bottom one, the C80 capacitor (16v1000uF) burst and the liquid ate the path that connects it to the board. Replace it and add some wires to connect it to the closest solder points on the board. (refrofix marbella)
Head servo not maintaining correct speed	Unscrew the top of the Betacord unit. On the SV-1 servo board, located right to the reel mechanism, locate capacitor C41 and replace it with a new one.
None of the buttons work, the clock doesn't flash, and only the PSU hums	The circuit board that controls the buttons (SY-2 board) had a large crack in it. It could be a cracked solder joint or damage to the board itself.
Temporary solution to stop the machine from chewing tapes	If you don’t have any spare idler tires for now, you can make the machine use the gear on top of the idler assembly instead of the idler tire. See the two metal tabs between the reels? When you press Start, those metal tabs move forward, allowing the gear to spin. When you press Stop, the tabs move back, stopping the gear and letting the idler take over. During this process, the gear keeps spinning. If you push that metal tab forward instead of relying on the idler, the gear will make it spin. By attaching something to hold the metal tabs forward, the machine won’t use the idler, and it won’t chew your tapes.
unlace issue	From Television magazine: In the Sanyo VTC5000 series replace the same idlers and change the value of the resistor (R49 on the syscon board) in series with the reel motor drive from 2.2R to 1R - it stands up on the top left-hand corner of the PCB, beneath a heatsink. And don't forget the AL switch.
Slow reel motor	From Television magazine: The reel drive motor used in this machine has a tendency to run slow with the result that tapes get tangled. Motor replacement is obviously advised but is neither cheap nor easy. I've found that a single drop of high-quality watch oil applied to the upper bearing, which is just accessible with the cover removed, can double the life of the motor.
Wont playback own recordings	From Television magazine: This machine would play prerecorded tapes all right but wouldn't play back its own recordings without having to adjust the tracking control from the click position. It has a small subpanel called the "control pulse rec/play circuit" mounted piggy-back on the main servo panel SV1 (this subpanel is not fitted on later versions). The fault turned out to be on this subpanel, which has to be unsoldered from the main servo panel before you can work on it. Oscilloscope checks revealed that the tracking pulses to pin 8 of IC4501 were of reduced amplitude and incorrect shape. The culprit was C4505, a tiny 1uF, 50V working capacitor which was virtually open-circuit. Replacement restored normal operation.
Random Stopping	From Television magazine: This machine would load when a cassette was inserted. It would then start to play. After about five seconds it would stop, with the tape fully loaded. The only function that then worked was stop. The tape could then be unloaded. Our main problem was that this fault was very intermittent. We had to spend a lot of time trying to instigate it. Attention was centered on the system control circuit. We found that when the fault was present there was no waveform at pin 39 of IC3001. The input waveform at pin 2 of IC3003 was correct and the culprit turned out to be W.G.L. Q3012.
Poor / no rewind/FF	From Television magazine: Sanyo VRC5000 and VTC5150 It seems that he Sanyo VTC5000 and VTC5150 form a large percentage of the Betamax VCRs in use. I fix more of these than any other single VCR model. They are exceptionally robust machines that go on for ever - apart from their one weakness reel drive. Poor or no rewind/fast forward is very common, even though these operations are done with the tape unlaced (unlike Sony Betamax VCRs). Usually the cause is a worn idler roller: the early ones had only six turns on the springs, but replacements may have many more. Nearly always only the idler roller and springs need to be replaced. This costs about £2 instead of the £5 for the whole idler assembly. A broken drive belt is fairly obvious and is simple to replace. The other common problem is a worn reel drive motor. This sometimes intermittently fails to run, restarting when the machine is powered down and up because of the large kick-start at switch on. T have on occasion dismantled a motor to move the brushes slightly to a less worn part of the commutator. This is not recommended, but it can work for years and the motors are expensive. A very important point is that here's a bug in the VCT500O's syscon. If it shuts down because it hasn't received reel pulses it proceeds to lace up! If there's no reel drive at this point to take up the tape, the result is a devastated tape. A customer who had put up with this intermittent tape chewing continued to use the tapes: it took a lot of effort to clean the heads so that the machine would work again. The VTC5150 doesn't suffer from this problem. Sanyo don't seem to have learnt their lesson from these otherwise excellent machines.
No E-to-E vision	For no E-to-E vision check relay RY1001 on board VD1 P.B. for dirty contacts.
Horizontal line on playback	From Television magazine: On playback there was a horizontal line three-quarters of the way down the screen - even with a prerecorded tape. Replacing the head disc didn't provide 'a cure so I tried swapping over the whole cylinder motor and upper cylinder from a VTC5300 (same unit!). This cleared the fault. Replacing the original upper cylinder assembly brought the fault back. On these machines the fixed head section of the transformer is mounted above the head disc in the upper cylinder: I suspect that the cause of the trouble could have been a short-circuit turn.
load / unload issue	From Television magazine: This model can exhibit similar threading problems to the VTC5300. but for a different reason. Reluctance to load and unload the tape in the 5300 is due to the drive belt and loading ring: with the 5000 it's due to wear on the gear clutch which drives the loading ring. The worm clutch must be replaced.
Intermittant stopping	from Television magazine: The complaint with this VCR was intermittent stopping. There was no sign of the fault when the machine was brought into the workshop, so we replaced the intermediate idler and returned it. A few weeks later the machine came back and this time we were able to see the fault. I still suspected the take-up drive -so did the microcomputer IC3001: pin 39, the take-up reel sensor input in, had a switching waveform on it but the waveform didn't reach 0V and was only 5V peak-to-peak with a 9V supply. Pin 39 is driven by the collector of transistor Q3013 which was not being fully turned on. The reel sensor output level was 2V peak-to-peak, a bit on the low side. After removing the turntable and cleaning the optocoupler the output increased to 6V peak-to-peak. Q3013 now turned fully on and the machine worked normally.
Mains fuse blowing	From Television magazine: No results with the mains fuse F5201 open circuit, a replacement fuse blowing - suspect the STK7216 switch-mode power supply i.c. (IC5101)
Eating tapes	From Television magazine: This machine grew hungry and ate a tape. After we'd removed the remains and cleaned up the tape path which had seen a lot of use - we slipped in an old tape and pressed play. The tape laced up and the head started to rotate. There was no tape take-up however. Further checks revealed that there was no supply to the reel motor. which is controlled by IC3006 (BA6209). As the supply to this i.c. was correct we decided to replace it. This provided a complete cure to the problem.
No colour	From Television magazine: The complaint with this machine was no colour. We so seldom encounter real colour faults on VCRs these days that we find ourselves a bit rusty when it comes to the principles of colour-under systems! It wasn't necessary to look very far in this case however. The fault was present in both record and playback, and we found that the signal from the sub-mixer in IC1006 (pin 30) was virtually non- existent. Both the sub-mixer inputs were present and correct - 4.43MHz at pin 27 and the divided-by-eight voltage-controlled oscillator output at pin 26. The voltages at pins 26-30 of the i.c. were also correct. so what was happening to the mixer's 5.12MHz output? It was getting lost in T1010. the first half of the bandpass filter. The tiny signal downstream at C1179 increased as we wound the core of T1010 right out: either this little transformer had developed short-circuit turns or the tiny resonant capacitor built into it had gone bad. Since the transformer is connected to the 9V rail there was no effect on the voltage at pin 30 of the i.c, A replacement transformer (part no. 4-259V-20800) cured the problem.
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