Power Supply U402 Voltage Readings; on pins 11. and 17. they are -11.98v (to ground), just a little under, can you identify a component from the supply side that I could check to see if it is under or over specification, this would be to achieve a little more voltage?

 

I do not believe the noise problem is related to the voltage readings. I think it is more likely to be poor connections on the connector to U409 or the connections to the read head. (Conn 10) If the noise is the same on both channels I would suspect noise on the power rail A5. This may be caused by C767 or R614 on board U405.

Les.

 

I brought the unit in and connected it to the pre amplifier to listen through the speakers and I also listened through a quality headset; I’ve listened very hard with the volume up and down and I am pleased to report back that there is no Interference Noise any more, many thanks for your professionalism on this one Les.

There is a little Interference Noise from the volume control on this unit; only when it is being turned around, and in a certain position this happens, I have tried once giving it a good spray of Kontakt Chemie: Kontakt 60 and a few days later a good spray of Kontakt WL and turning the knob after each spray to move the spray around inside.

I have uploaded a two old photos showing the rear of this control; there is access for spraying on the side and maybe from the centre of the end and info on Kontakt Chemie.

Can you kindly advice on this; I have a can of Servisol Super 10 which is solely for switch cleaning?

And could I beg of you for some help with post #181; I would like to fine tune some of these voltage readings with your help.

 

The Servisol MAY help but it could also destroy the potentiometers depending on the materials in the potentiometers and the solvents used in the Servisol. This is one component I would agree on replacing as the carbon tracks wear with use. (I do not agree with your general approach of replacing components on mass even when you have not proved them to be faulty.)
I don't understand why you are not happy with -11.98 volts on the -12 volt rail. It is only 0.17% out and I do not think it would cause a problem even if it was 10% out. The spec on the regulator that you used is +/- 1% (Which is better than most regulators.) If you want it better you will have to search for a regulator with a tighter spec or do a total redesign on the power supply.

Les.

 

The Servisol MAY help but it could also destroy the potentiometers depending on the materials in the potentiometers and the solvents used in the Servisol. This is one component I would agree on replacing as the carbon tracks wear with use.

I think you could be quite right on this and I have missed my opportunity when the unit was apart to replace this volume control, I think it is worth asking for a second opinion on this solvent maintenance, I will ask on the MFBfreaks.com forum and see what they have to say.

(I do not agree with your general approach of replacing components on mass even when you have not proved them to be faulty.)

I had already made the decision and spent much time finding out what was fitted, making lists, finding suitable replacements from different suppliers and lastly I did have them sitting here. I am already an old man and I am hoping that this renewing will last the rest of my lifetime, this is my logic.

I don't understand why you are not happy with -11.98 volts on the -12 volt rail. It is only 0.17% out and I do not think it would cause a problem even if it was 10% out. The spec on the regulator that you used is +/- 1% (Which is better than most regulators.) If you want it better you will have to search for a regulator with a tighter spec or do a total redesign on the power supply.
Les.

Could you kindly look at the voltage readings for A6 in post #180 there is a discrepancy with these two readings?

 

Remi who has given help before on MFBfreaks.com forum has made this comment

“Hi Michael, i'm sorry, i have no clue. It seems you have done all you can to clean the potentiometer.
Maybe the potentiometer is damaged on a perticular spot? maybe you can measure the resistance while turning?
Don't know what the result would be if this is the case, perhaps something completely different than your problem now.
It would not be the circuitry around the volumeknob?
regards, Remi”
http://forum.mfbfreaks.com/viewtopic.php?f=5&t=8426&sid=c309a48f3fe50bd4a423ced100828960&start=60

Les could you kindly advise on making resistance and voltage tests on this control to see if anything can be learned?

I had edited my latter part of my last post; maybe you haven’t noticed?

 

There is a Word document (this allows you to edit) and a PDF both having the same contents that anyone wishes to have a copy; they list all the Electrolytic Capacitors and Transistors.

This is the link to the folder https://drive.google.com/drive/folders/1hp1PI3J2M8gBpoGbOZu1wYY6xO1Ogp9k?usp=sharing

This link you can see the cassette player playing; the recording on this cassette was re- recorded in the 1980’s hence the second recording did not fully overwrite the first recording, I think this was done because the recording was a little poor.
To get the optimum recording; preparation is required by making sure the tape heads are clean hand wind the tape forward to clear the transparent tape, insert and press only the REC button, set the player going with the LP or CD that you are going to take a recording of and make sure that the monitor switch is set to position “Source”;

Then bring up both recording level controls so that the peak indicator +4dB is just starting to blink; both meters should just reach the red areas of the scale. (if you look at my left channel of the recording in this post the level meter it is a little lower than the right, the left level should have been a little higher, so it is better to have both levels reaching the same).
Some tracks when played workup to a grand finale which is higher/louder in this case it is better to play the track through, this gives a chance to alter the level controls, we call this setting up, to achieve clarity on the recording, after you are happy with the levels, then start your recording from the beginning.

https://drive.google.com/file/d/1Ajcya4Pw-WN0aswIavR-70B4sre094Jh/view?usp=sharing

Thank you Les for all your help and continued support

 

Hi Michael,
I pleased that you have cleared all of the faults. I had missed post #186 as I was on holiday when it was posted. There is nothing you can do with resistance checks to identify a noisy potentiometer. The only thing you could do is to check that there is no DC component on the input signal to the potentiometer or coming back from the circuit being fed from the slider. The track on the potentiometer just wares with use due to friction between the wiper and the track.

Les.

 

Cleaning the tape heads; you will need methylated spirits (meth’s), I have a nice smallish glass bottle to store mine, cotton buds 3" inch (75mm) long or longer would be better because access is limited due to the cassette holder being partly in the way and if you have large hands, even more so and kindly ask for a pair of your wife’s white cotton which is usually lint free pants all very important.

Using one cotton bud dip on end in the meth’s and gently polish/wet all of the top of the 2 heads (2 heads in 1 = 3 heads in total) the right-hand head has a depression near where the two heads meet, clean this part also going inline, on this part for about 20 seconds in total; then use the wet end of the bud and place it centrally inside the gusset of the pants, keeping it quite tight, gathering all the loose material and holding it with your last 3 three fingers in your palm leaving your thumb and index finger to hold the covered bud which should be wet from the remaining meth’s and be very gentle, polish up the heads again for 20/30 seconds in total.

Use the other end of the cotton bud which is dry and place it centrally inside the gusset of the pants over a dry area not soaked in meth’s and holding it as before, polish up the heads again for 10 seconds in total. If you then avoid placing a cassette in for 5 minutes, to be sure the heads are completely dry.

Note; if you play a cassette for a few seconds and mentally listen before cleaning you might be very surprised at the results of the cleaning, even if the heads look clean.