Sony TC-177R deck buzzing, no sound

Today I've attached some small speakers just to briefly check sound from the deck.
Unfortunately, despite playing both directions, rewinding, fast forwarding, fully functional auto-reverse, functional recording (I can see peeks on spectrum analyzer when I play blank tape with recorded section) but I get no sound at all. Tired with an album tape too.

There is just buzzing as long as deck is connected to amp, from where it gets the power too. So, it is not the buzzing transformer, because tuner sounds great. once the deck is disconnected, and there is no buzzing when I switch to empty aux or phono ports.

All mechanical functions on deck work perfectly even via remote, which is a "WOO-HOO" give the age of device and complicated controls, wiring etc.

I have another PB from deck I got as for spare parts, but reconnecting all wires, including ones that are not connected via connectors but soldered, doesn't seam to be wise idea at the moment.

I guess that problem is most likely on the PB, but I've cleaned it with medical alcohol already, when I was fixing the mechanical parts. I have the service manual.

No idea where to start from, although it smells like something short-circuited on the PB. Perhaps someone already had similar problem and gained experience how to overcome it.

Any hint would be appropriated, but it is nothing urgent or important. If, when, than...

Update

I was doing a bit of "no no" - marked the positions of potentiometers on PB, than worked them a bit, and I got the sound!

Than I heard that capstan motor is rotating too fast, and adjusted its speed.

I've also adjusted the position of head for both directions, using original album tape.

Still, constant abnormal buzzing is present, regardless on mode of deck. stopped, paused, playing, rewinding, forwarding, recording.
I wasn't able to neutralize it with anything I could think of. I have to turn volume really high in order to make "space" for the sound reproduced from the tape.

One thing might be an important detail for those who are pros in this (unlike me) - the buzzing doesn't increase when the volume is increased, it is constant, no matter if the volume is 0 or increased to any level.

I think this narrows the possibilities relative to my previous.

I love these monologue threads

Been reading some tips on technical advices sites. Most of people suggest extra wiring for grounding of deck chassis, since they think that bad grounding cause the buzzing. I've tried it but nothing changed.

Since there is no buzzing until speakers are connected, it is definitely not buzzing coming from some part of the deck like motor or so. It is some audio interference.

What I'd like to try next is to demagnetize the head, but I've never done that before, and I don't even know if that makes any sense, given to symptoms.

LJV said:

I love these monologue threads

Been reading some tips on technical advices sites. Most of people suggest extra wiring for grounding of deck chassis, since they think that bad grounding cause the buzzing. I've tried it but nothing changed.

Since there is no buzzing until speakers are connected, it is definitely not buzzing of coming from some part of the deck like motor or so. It is some audio interference.

What I'd like to try next is to demagnetize the head, but I've never done that before, and I don't even know if that makes any sense, given to symptoms.

Click to expand...

Try cleaning record bar and is there a program button to switch cassette side while in unit? If so the switch could be dirty and needing cleaning. Most issues are from dirty corrosive switches from sitting for years causing the noises

All switches on the unit are micro switches, identical to those found in computer mouses. They all work , and all the deck functions work via remote control too.

Besides, the buzzing is present even when cassette is not in the unit. It is constant regardless on presence of cassette or engaged function.

Does this unit have the head that spins for tape direction? If so, the wires leading to head could be broken causing both no music and the humming

baddboybill said:

Does this unit have the head that spins for tape direction? If so, the wires leading to head could be broken causing both no music and the humming

Click to expand...

Yes, head spins, cables are checked, but I've wrote in my second post that I got the music after working the potentiometers on the PB. Music sounds as if it is a microphone recording of the music played by another device. Sort of like in the distance, or far away. I hope you get what I'm trying to say - sound isn't direct and dominant, appears almost as secondary relative to buzzing. On the same volume level, tuner blasts, while original tape with music can't break trough as it should.

So music plays but sounds distant and there is still buzzing?

baddboybill said:

So music plays but sounds distant and there is still buzzing?

Click to expand...

Exactly.

Post a short video because of buzzing your hearing

LJV said:

baddboybill said:

So music plays but sounds distant and there is still buzzing?

Click to expand...

Exactly.

Click to expand...

Try looking at the rec playback switch if the unit has one. Im not sure- it depends on the mec but some domestic stuff used to have switches that enguaged within the mech when rec/pb button was pressed that not only switched the different voltages to the motor but also the audio signal path flow. Cruddy switching in a rec/ PC switch can easy give you low audio, introduced noise and also cause recording over pre-recored tape (if you also have a crap record tab sensor switch)

If you can find it DEOXIT!

Z

Zedman said:

LJV said:

baddboybill said:

So music plays but sounds distant and there is still buzzing?

Click to expand...

Exactly.

Click to expand...

Try looking at the rec playback switch if the unit has one. Im not sure- it depends on the mec but some domestic stuff used to have switches that enguaged within the mech when rec/pb button was pressed that not only switched the different voltages to the motor but also the audio signal path flow. Cruddy switching in a rec/ PC switch can easy give you low audio, introduced noise and also cause recording over pre-recored tape (if you also have a crap record tab sensor switch)

If you can find it DEOXIT!

Z

Click to expand...

Unfortunately, it is all digital.

Thanks for the thought anyway.

Looks like you may be at the start of a fault finding journey. I hope it all ends well.

Z

There's one thing I could try, but I'm not sure if it could be related.

There are 2 big transistors with coolers on the PB, and one on the chassis. The one on the chassis was dead, so when I've replaced it, it gave back power to deck. I have two spare transistors to replace remaining ones, but it is delicate, the PB is old, and unless if it smells like possible cause of the problem to someone who really digs electronics, I'd rather not touch them.

Any thoughts? Is there a way to check them without removing them from PB. Some DIY trick with no special equipment?

Hey LJV, you could use a multimeter and check for low resistance cross he transistors legs. Very often they will short circuit when they fail. It is possible that a low resistance reading may be from other components close to the transistor in the circuit, however, any resistance of less than 10 ohms should be further investigated.

If you need to remove the transistor then solder wick or a solder pump will most likely be needed. Practice on an old board if your skills need development.

A solder pump, wick, soldering iron and multimeter are essential tools for electronics servicing. All up the lot would cost about $30 off te net.

Hang in there!

Z

Zedman said:

Hey LJV, you could use a multimeter and check for low resistance cross he transistors legs. Very often they will short circuit when they fail. It is possible that a low resistance reading may be from other components close to the transistor in the circuit, however, any resistance of less than 10 ohms should be further investigated.

If you need to remove the transistor then solder wick or a solder pump will most likely be needed. Practice on an old board if your skills need development.

A solder pump, wick, soldering iron and multimeter are essential tools for electronics servicing. All up the lot would cost about $30 off te net.

Hang in there!

Z

Click to expand...

Thank you for the multimeter tip.

I've been soldering since I was a teen, which more than a 25 years. I've even done extremely precise soldering of tiny elements on PC main-boards.
What scares me is the age of the PB, which is also +25 years.

What I noticed is that coolers of transistors do get warm (if that is any sign of functional transistor)?

Heat sinks are designed to dissipate heat so warm is ok. Hot is most likely not. The rule of thumb works well for temp most times- if you can't leave your thumb on it then it's over 50 degrees C and that's most likely indicative of a fault.

I'd really be surprised that an old PCB is fragile- mostly they have better copper than new stuff. SMD multi layer boards are a real nightmare!
Sounds like you have your technique down and maybe a bit of confidence is all you need.

If you progress carefully and take your time I'm sure things will work out. Lifted tracks can be fixed. What's the worst that's gonna happen- your in working unit remains in working???

Give it a good shot and you will do well.

Z

Sorted it out today.

It was the damn flat cable. The cable itself wasn't damaged, but cable's end isn't soldered to pins on connector. There is just a row of tiny sharp clamps at the connector's back into which the flat cable is pressed, so they simply cut the insulation to make contact with the wire. I've just repressed it, and it works like a charm. No buzzing, sound is loud and clear, it plays, records, recordings sound great too.

Nice work!

Z