Ferrograph part missing?

[sparkymike]

Valve V6 should be an ECC 83. The valve in the recorder is an AT7. An AX7 would have been better match to the correct valve I believe as the AT7 does not have as much gain. Loft safari to the valve pile I guess.
Mike.

[sparkymike]

Tried an ECC83 but no difference. Guess I will have to check component values around that valve first.
Mike.

[barrymagrec]

V6 should be an ECC82 / 12AU7.

[sparkymike]

On the series 5 circuit diagram I have, V6 can be either ECC82 or ECC83.
Can not find any circuit or any information for the series 5 A , so for time being I am using the one I have.
Mike.

[ms660]

Page 52 of the Series 5 manual....V6 = ECC82.

Lawrence.

[DMcMahon]

The 5A documentation I have seen shows a ECC 82, I have not seen any documentation for the 5B.

The ECC 83 is a pin compatible high gain version of the ECC 82 but not sure of its compatibility in the Bias Oscillator circuit.

If record erases an existing recording then that goes some way to indicating that the Bias Oscillator maybe functional.

David

[sparkymike]

You are right. Chassis is stamped with ECC 82 !!
AT7 now in place, but no change.
On record, an extra valve is used. Which one is that ?
In the manual there is a section that tells the operator to fit a shorting plug in the first jack socket, when using socket 2 with certain imputs. I have not tried that yet. I have been trying to record from the earphone socket of a small Sony radio. I do have a couple of Mikes somewhere so could try those and see if there is a difference.
Mike.

[ms660]

Originally Posted by sparkymike

On record, an extra valve is used. Which one is that ?

Referring to the schematic, there's two, V6 and V5, the ECC82 (the bias/erase oscillator) and the ECC83 (the detector/amplifier for the record level meter) they both share the same HT feed which is switched in when in record by SW1-1c, the route from the main HT filter capacitor is via pin 6 of P3-SK3, SW1-1c, resistor R2 and pin 7 of P1-SK1, from that point the HT is fed to V6 via pin 4 of P4-SK4.

The bias is supplied to the tap on the record/playback head via capacitor C5, SW1-3c, pin 4 of SK3-P3 and the erase/bias link P8-SK8.

The record signal to the head from the amplifier is via pin 8 of SK1-PL1 and SW1-3a.

If that's any help.

Lawrence.

[sparkymike]

Hi Lawrence, thanks for that info, could be a great help. It does seem like amplification is down, so will change those two valves first I think.
Re the main switch, are the banks numbered in any way ? Is bank 1 the top one nearest the base plate?
Mike.

[ms660]

The poles and contacts are shown in the switch diagram, I would say bank 1 is nearest to the plate (the front of the switch) from the description and the photo in the manual.

Lawrence.

[sparkymike]

I removed the power unit from the base of the cabinet to check the two resistors R42 and R43 and apart from them, no other similar parts underneath.
They should be 10K but both a bit high, one 11K and the other 12K.
Would this affect things or do I leave well alone?
I must say it looks pretty clean under there with no corrosion worth mentioning.
Mike.

[Welsh Anorak]

I doublt that small increase in value would make any difference. If you're doing a full resto then you could chnage them but I'd leave them for the moment while you trace the fault. I'd have a look first at how your machine differs from normal - possibly something was removed or changed by the previous owner.

[sparkymike]

Hi Glyn, I think I have removed the additions by previous owner. All what is left looks to be original factory wiring apart from a neon indicator that is wired across the mains input Bulgin plug for some weird reason !! The bulbs that light up the recording meter may have blown and that might have been a quick fix to tell him mains was present in the machine..
I will have to wait until dusk to check those bulbs. What type are they?
Mike.

[ms660]

In the manual the two bulbs are listed as L.E.S. 6.5V .15A.

Lawrence.

[sparkymike]

Bit of luck, I found I had a card with around eight on it !! Need a magnifying glass to read the voltage though. I just tried another go at recording and on playback with volume full up you can just hear it. Could a faulty head do this ?
I suppose it could even be bad switch contacts somewhere along the chain, although I have dosed the wafer switches in switch cleaner and rotated the switch many times..
Will have to do a systematic check.
Mike.

[ms660]

Are the relevant plug and socket contacts ok?

Does the level meter indicate as it should on record?

Lawrence.

[sparkymike]

Level meter is reading very low unless volume control is turned right up.
I am about to checksome of the plugs. Those on the power section look very clean, but I still gave them a wipe over. Now goint to look for P2.
Mike.

[sparkymike]

From P2 plug which fits into control panel, to record/playback head terminals I am getting 40 ohms with deck control switch on record.
Mike.

[sparkymike]

Following Lawrence's advice, I checked through from deck to control panel and when checking the octal plug lead, no.8 pin/wire was o/c. Lucky for me it was not in the middle of the cable so managed to remove old wire stub from the plug terminal and grafted in a new piece of wire and soldered it to a stripped back end of the black wire. Not enough room to heat shrink it but fitted the stretch sleeve ,that is around all the cables,over the joint. Playback now good with plenty of volume. I can only think that when I got very faint playback before, the wire must have just been in very close contact to record anything at all.
On rewind, it slows down near the end of the tape, but all the Ferrographs I have had before, did this, so not too concerned. Possibly pressure pads too hard on the heads?
Thanks for all help,
Mike.

[ms660]

I wonder if that extra pot is anything to do with the pots referred to in Sections 10.1 or 10.2 in the manual.

Lawrence.