Old ('60) italian ECL82 Record Player on the bench (FINAL - UPDATE)

[kagliostro]

I've on the bench an old italian Nuova Faro Record Player that uses ECL82 tube

a friend gived it to me to be repaired, as always is near impossible to find schematics

so I reverse engeneered the circuit to have the amp section schematic



My friend told that the (on the schematic 220R) resistor between the 160v AC and the diode was burnt and someone give him a 220R 2W resistor to put on, he tried but this new resistor smoke when the amp is lighted on

Till now I've find that the diode is shorted, I tested the tube and on my tube tester it is still in very good shape, with my speaker impedency meter I measured the impedance of the OT and it is around 4K (3.94K at the test frequency) with the original speaker connected, the double e-capacitor seems OK (measure open with ohm meter)

Have you any council about other test to perform ?

--

One other thing

As very often happens on this old record players, there isn't a real PT, they used an Autotransformer and, bad on the bad, one side is connected to ground also pin 4 of the tube (heater pin 4) is connected to ground, the potentiometer shaft (that is metal) result to be connected to ground (and to the line, see schematic)

I would like to disconnect the Autotransformer from ground and to leave it floating, do you think there are disadvantages ?

Whith this arrangement is possible to use a virtual CT on Heaters (2 x 220R resistors) and to connect it to the cathode of the Pentode ?

Is possible to put on a Bridge instead of a single diode ?

Thanks

Franco

[John]

PRR will probably know this: I'm wondering why the 220 ohm resistor is there coming straight off the 160 AC. Why not just hook into the 140 V winding if you want lower voltage? And it doesn't seem like a 2W resistor would be nearly heavy enough anyway?


I assume you've already tested the filter caps to be sure they're not shorted or leaking badly?

[sluckey]

Till now I've find that the diode is shorted... Have you any council about other test to perform ?

Check for shorted filter caps (or just go ahead and replace them.

Fix it just as it is for now. Then worry about "improving" it. Don't play guitar thru that amp yet.

[shooter]

this might provide some insight for an R in AC

http://www.animations.physics.unsw.edu.au/jw/AC.html#resistors

[kagliostro]

The original resistor was burn open and colors are unreadable (unreadable also the other resistors of the circuit also if measured they result to be on spec with "standard" ECL82 amp values)

so the value is now 220R 2W, the resistance value before burn is unknown and the W was 1W (I suppose looking to the dimension of the burn carbon comp resistor)

Really I don't know the reason for the presence of that resistor (thank Shooter for the link, I'll read all with interest)

May be, as there is a voltage selector, they want to have a specified AC independently with the line voltage selected (?)

I know that a resistor can be put between AC and vacuum tube rectifier as to reach a specific resistance required for a specified tube

and, also, I've one amp whith resistors between AC and SS FWB, but there the situation is very different

--

Yes Steve I'll fix as it is and as record player, it is not planned to be a guitar amp

I regret I haven't an ESR meter, but measured with ohm meter the two sections of the e-cap (40uF + 40uF) seems to be OK, no short on it, I think I'll go to replace the double e-cap, the problem is that it is double and small enoug to be difficult to find one, so I must put on a pair (on a small space)

--

Oh, any idea about what mean the E on the 1M-E pot ? BTW I don't remember a control tone arranged that way, someone has seen it before ?

Thanks

Franco

[shooter]

no clue for E, although my smart A brain thinks "everything" as it appears to control both Volume and tone

[PRR]

It is Hot Chassis. This "may" be OK for a record player, if the pickup connections can NOT be touched. And if ALL touchable metal is insulated from the DC power. As said, no guitar!! And don't try to adapt it for iPod.

"Floating" the autotransformer won't work. It needs a real transformer.

Yes, if your line is over 220V,tap-down to get a reasonable DC voltage.

The 220r is smoking because either the diode or first filter cap is short.

The 220r is there because the diode has low peak current ability (and the autotransformer has low internal resistance). With a fat modern diode you may not need the 220r; but I'd leave it stock.

The tone control uses capacitor loading against the first tube's plate resistance. No clue on the lettering.

[kagliostro]

Many Thanks PRR & Friends for the answers

The bad thing is that the shaft of the pots are metal and there is continuity to ground

chassis is wood and the knobs plastic, but between chassis and knobs there is an unprotected nut and a small part of the thread of the pot

--

Look to the pot/switch, one of the two wires coming from the line enters one of the pin of the switch and exit in an unshielded wire that is connected to a small metal shield via the pot shell and the shield is connected to GND via the GND connection of the spy light bulb







OK, I'll leave it as it is .... but I don't like ..................


or ............ can I disconnect the spy lamp from the pot shell and leave it only connected to GND (on PCB) and connect the line that arrives via the switch directly to PCB GND and disconnect it from the pot chassis ??


Are there problems if I do that ? ..... missing shield function on the pots if the shell is not connected to GND ?? Can I connect the pot shell to GND using a capacitor ??


Thanks

Franco

[sluckey]

Is the power cord polarized? Or is that even an option in Italy? In the USA there are two prong polarized AC plugs. One blade is wider than the other so the plug can only be inserted one way. It cannot be reversed. If this is an option just be sure the neutral is connected to the correct blade.

[kagliostro]

Ciao Steve

This are the kinds of electric sockets we use here and all are full reversible



The Record Player has a 2 wire cord, may be I can swap to a 3 wire cord (withot the use of an IEC socket because the Payer is old and it will be not nice to see one there)



The 3° (GND) wire I think that can be connected to the small metal shield that holds the pots (if I disconnect the pot and shield from GND on the PCB), what about this mod ?

Franco


p.s.: I forgot, we have also other socket like this (and they are not reversible) but you can find it only for industrial use, not at your home

[PRR]

1) insulate ALL metal against finger contact

2) add a GFI/RCB ground-fault shock preventer (here we can snip them off dead hair-dryers) (EDIT-- a dozen pages of Amazon.IT tells me that hair dryers in Italy do not have GFI plugs, as has been required in the US for a while,image.)

3) (best) add a 40VA 230V:230V Isolation Transformer (now you can play iPod or guitar without shocks)

Does he really need a cheap record player?

[kagliostro]

Yes, here GFI plugs are unknown 


But in all the house the electrical system must have a (usually 30mA) differential switch



https://www.campoelettrico.it/blog/3/interruttore-differenziale

Does he really need a cheap record player?

I think it is something that the brother of his wife has at home since a very long time and so they are attached to it

Thanks PRR

Franco

[shooter]

they are attached to it

emotionally or 220 50hz

[kagliostro]

 

[kagliostro]

I've find the correct info about the E on the pot (and verified it as to be exact)

E means Logarithmic (on old Lesa and Liar italian brands)




Franco


p.s.: A friend has just linked me this .pdf file

[kagliostro]

Long time is past, casually I happened to be on this thread and I've seen that the final schematic was missing

The Player was maintained as original, no insulation transformer were used (on the Player were adopted attentions as to result a double isolation unit)

But there was a problem, now, in the area where lives my friend Line voltage is around 245V instead of the old italian standard 220V, and the change voltage had a 240V option but the PT no and if you turn the change voltage to the 240V option in reality the connection was done to the 220V intake of the PT

So I adopted this "trick" and my friend can hope to use the Player for other 20-30 years 

Here is what I've done



And till now it is in good shape

Franco