EM84 Saba villingen 125

[chokesrule]

Hi Lawrence so are you saying the service sheet is wrong or my measured voltages on the ebf89 are wrong?thanks Alan

[chokesrule]

Hi Lawrence, are you saying the service sheet figures might be wrong ? Or my measured voltages are wrong? Is this why some one has changed r10 from 3.3k to 1.5k?. My understanding of electronics is very poor. Thanks Alan

[ms660]

Originally Posted by chokesrule

Hi Lawrence so are you saying the service sheet is wrong or my measured voltages on the ebf89 are wrong?thanks Alan

To me, yes the service sheet seems wrong, doing the Ohms Law seems to suggest that.

According to the schematic voltages for AM I make Ig2 (the screen grid current) for the EBF89 approx. 1.6mA which for no signal conditions would be way off according to the valve data.

Lawrence.

[chokesrule]

I tried looking at the curves, i cant make any sense of it, from the valve data sheet what should it be? Thanks Alan

[Joe_Lorenz]

Hello,

generally speaking, it is not unusual that one finds a switch problem due to oxidation or corrosion of contact point surface. This causes resistance in the switch - and that is not good at all!

It is not the worst idea to clean all contact points before changing components randomly. There are a lot of contact cleaning spray cans available, though I prefer "Tuner 600" and "Tuner Trio" from Kontakt Chemie, but any other brand may work as well.

Kindest Regards, Joe

[chokesrule]

Hi thanks for the advice Joe.

Look what i found ! Follow the small tool in the picture. that is a solder blob on the end of a wire and its in mid air, hard to tell exactly what it is, but has it come away from a switch contact?..The wire runs to lug 3 on filter 2..Why have a 20mm of tinned wire hanging in mid air?.The only way i can see if that wire with the blob on it should be connected to something is remove components in that area. Too risky when its late, will look tomorrow.

[Joe_Lorenz]

Hello again,

according to the wiring diagram, lug 3 should only be connected to a wire going to switch U6, no other component. Maybe the wire had been cut a bit too long? German manufacture does not necessarily mean perfectly built, sorry to have to say this.

Regards, Joe

[chokesrule]

Well the wire turned out to be a solder blob which had ran down the contact during manufacture.I was hoping so much that this was going to be the answer to the low voltage, it would of been so simple! It had lifted when i started to clean the piano key contacts as best i could. This then led to a day of hell, i tried to clean the contaxts as best i could. I could not figure out how to completely remove the sliding bars and when i put everything back together i had lost FM. It took hours to get the contacts to work again. However i have slightly better other frequencies. I removed the can covers of the IF transformers could not visually see anything amiss . I checked the resistors as best i could ,they seem ok. If there is anything wrong here i do not think i have the dexterity to rebuild these units. The wires are hair strand thick.mi checked the FM tuner, all seems ok. So ordered an EBF and ech, that's all i can afford right now, but just on the off chance thought i would give it a try. But now not sure if these switches have some role in voltage loss. Its very hard to safely measure what's going on there.

[ms660]

Your measurements given in Post#15 seem reasonable, so far as I can make out they broadly tally up with the EBF89 valve data.

But to be sure check C22 for leakage and check for any leakage between g2 valve socket tag and ground.

As said before, the screen grid voltage and current relationship given on the schematic looks wrong to me.

Schematic:

g2 voltage = 115V.....g2 current = 2.5mA, therefore the voltage drop across R9 (47k) = 0.0025*47,000 = 117V.
115V + 117V = 232v.
HT given as 190V.
Does not tally.

Lawrence.

[chokesrule]

C22 is the wierd capacitor right up close to the ebf. Just to double check me ,4.7nf is 4700pf, so put a russian silver mica in. No change. I can't detect any leakage to ground from pin 1 either.

[chokesrule]

On if transformer 3, if I test continuity with a multimeter should i get a beep if i put positive probe on pin 3 and negative on pin 9? I dont get a circuit

[ms660]

Definitely if diode GR3 is S/C.

Possibly if it isn't. (I've never used a meter with a continuity test beep function so can't be sure)

The circuit is the FM ratio detector.

Lawrence.

[chokesrule]

Its got to be working then, fm is the strongest voltage to the em84 and is the best listening. Thanks tho lawrence

[chokesrule]

Same with the bass, if i press the dial into the radio. Boom there it is a whole load of bass. All these years ! Never even bothered with them! Was just happy with what it was!!, Its miles better than i ever knew!

[chokesrule]

I got it back to front. Its the bass potentiometer that has no cover, and i have not fixed it very well, the contact is not touching the track very well, and the bass fades in and out in the audio and you can hear how good it sounds and then it fades out. Got to fix this somehow! The radio is miles better than i knew!

[Herald1360]

Originally Posted by chokesrule

On if transformer 3, if I test continuity with a multimeter should i get a beep if i put positive probe on pin 3 and negative on pin 9? I dont get a circuit

Depends on the meter. My old Fluke 77 has diode check and continuity beep on the same function. A low resistance or s/c gives a continuous beep but a forward biassed diode just a momentary beep with a reading of the forward voltage. In this case, measured the other way round or using the ohms function either way round would show o/c for an OK diode.

[chokesrule]

Can anyone tell me what a 3+3M potentiometer is and describe in lay man terms , what happens to the sound as it goes through the 3 potentiometers. I am taking it:_
P1 is the treble
P2 is volume
P3 is bass

And why, if i turn the bass to minumum the volume gets loud and will not silence if i turn the volume pot all the way down. Some one has worked on this area of the radio, because p3 has old tool gnarls and there was those missing capacitors in that area of the circuit.

Can i hot wire p3 out of the circuit to give me max or nearly max bass because it is not working correctly and it drastically affect the quality of the sound. Until last night i did not know the radio could sound as good as it can .

[chokesrule]

The circuit diagram does not match the circuit board c43 in the diagram is connected to r37,, on the actual board it is not. The ledt hand side of r37 is earth . Or! Should there be a wire from the centre tab of p3 to the binding post shown to the right of r6?

[ms660]

Yes, the left hand side of R37 in the PCB layout is ground, via the screen of C33.

That discrepancy between the schematic and the PCB layout is also replicated in the Villingen 9:

https://nvhrbiblio.nl/schema/Saba_Villingen9.pdf

But the PCB layout concerning the capacitor (the low value pF, C43) from pin 6 of the output valve in the Villingen 125 and the Villingen 9 follows the same regime as the schematic for the Sabine 14 insofar that it connects to the triode side of the 220pF coupling capacitor not the pentode side:

https://nvhrbiblio.nl/schema/Saba_Sabine14.pdf

…..So far as I can make out.

Lawrence.

[chokesrule]

So should i move c43 over to r 36? Would i cause damage trying? If i plugged the radio into a current limiter?