do see one error on this schematic, but hope that it is only being on the "snippet" that is shown just above, and that you do not now have it incorporated within your circuitry, as it would have to have been a deliberate add on..
Look at the 9VDC power input and you see it being routed to 4 connections:
- The R27-30 resistor junction
- The emitter of V9
- The Positive of C36 electrolytic
- The junction of the - of C35 and the speaker +
The last line/wire has a round connection node on it, but a check of the full schematic will show that line to actually be an outer border line, defining the circuitry that is being within the A8 board of the set.
Therefore there is no connecting wire and hope that you have not put one in circuit.
That line shows that the circuit represents the A8 board, it has no electrical use. I forgot to delete it when I made the snippet.
The last test given was to see how the unit was operating after those two filter components were
subbed in and a max volme test on the unit..
Since this is being a single ended supply design and not a dual polarity supply it is usually not
a problem of your C38 and C35 filters of having an ESR factor and not adequately filtering off
high audio frequencies. Plus, I gave full credit for new capacitorsnow sitting those slots.
With high ESR presence parasitic ultrasonic oscillation can occur and both distort / modulate the audio waveform and thereby additionally cause an inordanite increase in current consumption due to the high waveform duty cycle with all of those mixed in high frequencies.
You usually only see this HF circuitry used on the output stages of differential output stages or modular IC output stages. So you say . . . .No correction found . . . . . .
I'll make a snippet later showing the actual values of the capacitors that I replaced with the old ones.
From what I remember, C36 was a 1000uf cap and C24 a 500uf. I replaced them with a 1000uf and a 470uf, even though on the schematic, C36 figure as 2000 ufds.
Looking at the radio, I realised, This unit looks like a vef sigma 260, but on the inside
is not.
Why that? Because I have another older, lower quality vef sigma 260.
When servicing on this unit, I realised that the boards are different from the older one. Even the mains connector is different.
It turns out that, the casing outside is of a vef sigma 260 and on the inside is of a
vef 260-2.
What are the differences between them? They are
almost the
exact same. Firstly, the quality,(it is made
for export) then the circuitry.
Let me show you:
The casings (they are the same)
The amplifier-preamp-tape record board
and the power supply:
What led me to think that this is a vef-260-2 board, is the replacement of the 8pin top hat ic with 2 transistors, and various differences of the component placements on the board.
Now, I shall supply you with the schematic of the vef 260-2, you'll see that it matches these differences, especially the replacement of the ic with 2 transistors in the tape recording section.
There are 2 versions of the schematic, one both in English and Russian, and one only in Russian, but with far better image quality.
English-Russian:
https://photoland.io/i/PncrG or
https://pli.io/PncrG.png
Only Russian:
https://drive.google.com/file/d/1CQbBrZGc2Viuvk_ajdlcYoUt1Di2vx2F/view (zoom by scroll wheel, you can download too)
You'll see that the amplifier section is almost the same, I saw that C40 is also added there.
When replacing the caps, I wondered, where this c40 goes, because, on the normal vef sigma 260 schematic, it isn't there.
Also look at C36 on the full schematic, I think it switches on when on radio and off when on tape, pay attention to the RADIO/TAPE (that is also the on/off) switch and AFC/LIGHT one too, and follow the points.
I suggest you first consult the English schematic, then, if something is unclear or not easily readable, you check the only-Russian one.
Those russians, couldn't they use the vef 260-2 case...
How a vef 260-2 case should look like: (I personally like the case that I currently have, it looks older)
