No audio when playing tapes on a Sony Betamax SL-HF1000

[Draco_Red]

I've been having problems with a Sony Betamax SL-HF1000 that I recently came across. It'll play video fine, but it's as though there's no audio track on the tapes. When I put signal in the Line In, it passes the audio to the Monitor and Line Out ports and it shows the volume on the levels display. However when it plays a cassette there's no audio out and the levels display is flat. This is happening on multiple, known good tapes, and even on a new tape that I bought to record to and play back from for testing.

Since I've eliminated the tapes, TV and cables as being the problem, it has to be something internal to player. I'm not sure if there's a separate head for the audio track that might be at fault, or if there's something with the circuitry that processes the audio signal that has failed.

Any help would be greatly appreciated, thanks.

[johnmeyer]

I have a much earlier Betamax. In looking at pictures of your unit,







I see a LOT of switches that affect audio. They are located behind the two front-panel doors. Both the "normal audio" and "main/SAP" switches could mute the video if put in the wrong position. There are also audio sliders. Finally, I note that there are some line and mic inputs. If there is anything plugged into these jacks, it could mute the audio.

[Draco_Red]

Yeah, I've been pouring over the manual for this unit all day and checked to make sure that all the switches are in the correct placement and the sliders are at the recommended setting (middle for both right and left). Nothing plugged into the mic or line inputs, just the the cable going from Line Out to the TV at the moment.

[JVRaines]

What kind of audio is on your tapes? Just linear or are they Hi-Fi?
Have you cleaned the stationary and rotating heads?

[wulf109]

It's not a head problem as beta HiFi is recorded in a gap in the video track. It could be audio if your trying to listen to the normal audio track. The normal audio track uses a separate stationary head for audio. Early beta retail tapes had no hi-fi audio,just the normal linear audio track. The SL-HF1000 has separate monitor and audio output jacks have you tried both sets?

[JVRaines]

Ah right, the same heads record audio and video in Betamax. If the meters aren't moving on known-good Hi-Fi tapes, then there's a problem with the electronics.

[Draco_Red]

That's the conclusion I came to as well, but any idea what's wrong with what part of the electronics? I've done a visual inspection and couldn't find anything that's visibly failed (burnt chips or blown capacitors), but that just means that whatever's failed did so in a way that I can't see

[johnmeyer]

90% of "electronic" problems are actually mechanical, especially when it involves older equipment, and even more so when the equipment has been idle for a long time. Switches corrode and are the most likely cause of problems. While you cannot access all the internal microswitches, I would recommend operating each front or rear panel switch 5-10 times. I'd also find a plug that goes into each "line in" and "mic in" plug and run it in and out. There is often a switch that is part of the plug so that when something is plugged in, the unit uses the audio from the external source. This is especially true on your unit which has all sorts of dubbing capability, and therefore is designed, when set in a certain way, to record over the existing audio track using the external input. I would be tempted to hook up something to that external input and see if you can get the sound meters to show some activity. This would confirm that at least part of the audio path is operating correctly.

Most capacitor issues happen in the power supply, and if it was bad, you wouldn't be getting picture.

[Draco_Red]

Yeah, I just tried that, it seems like it just doesn't want to play back the audio track from the tape. When I plug in the composite out from an AV source it shows activity on the meters and passes the sound from the line ins to both the monitor and line out audio ports. Also tried a microphone and it recognizes it shows the activity for that as well. It's just as though the connection from the cassette audio signal is cut. I've even tried it with the "EE" button while a tape is playing, no audio from the tape, audio as soon as it switches to the live line in.

The only reason I was thinking capacitors was because in my reading about this it looks like the light blue Sanyo caps that were used in a lot of these are defective.

[wulf109]

Try the RF output jack,does that work?? If you get audio via the RF connection,that would help narrow down the problem.

https://forum.videohelp.com/threads/324502-Repairing-Sony-Betamax

http://www.usaudiomart.com/details/649018850-sony_hf_sl1000_betamax_for_repair/images/483931/

[Draco_Red]

Same thing with the RF jack; it'll pass through audio from the inputs, but no audio when playing tapes.

[Cornucopia]

EE (electrical to electrical), aka BYPASS, is easy. Full throughput via record+playback is much harder, so I'm not surprised. Johnmeyer was on the right track. IMO, too much effort for not enough return: don't waste your time any further - get a different machine.

Scott