Vortexion reel to reel tape recorder WVA series 5

[Luxman1050]

Two interesting things thete is supposed to be a variable resistor for bias. All I can find is a coil with adjustment on it or there is a unit on the back of meter marked VF not sure what that means but someone has undone the screw on base of it quite a bit. So maybe that needs setting. But all I can find on one of the schematics is a bridge rectifier there? Did not know you could adjust them? CT is fine.

[barrymagrec]

On a Vortexion the bias pot is on the front panel at the top surely?

[Luxman1050]

Yeah it is but the pot is supposed to be linked to a variable resistor in circuit under chasis and it's not. There's a 100k fixed resistor. So basically if you turn the bias dial as far as it can go it will only go to 50 on the meter not upto the full 500. Bias setting is supposed to be 150. Not 50 which is as far as it will go. So something along circuit needs tunning. On back of meter looks like an adjustable bridge rectifier as it has the 4 terminals with a screw underneath it.

[ms660]

Originally Posted by cdm1christopher

Yeah it is but the pot is supposed to be linked to a variable resistor in circuit under chasis and it's not. There's a 100k fixed resistor. So basically if you turn the bias dial as far as it can go it will only go to 50 on the meter not upto the full 500. Bias setting is supposed to be 150. Not 50 which is as far as it will go. So something along circuit needs tunning. On back of meter looks like an adjustable bridge rectifier as it has the 4 terminals with a screw underneath it.

I'm confused by what you say.

Lawrence.

[Luxman1050]

Here you go a picture of the so called bridge rectifier on back of meter which has VF stamped on it and there's a small screw on the base. Thats wired into bias dial.

[ms660]

So are you saying that the input to the bridge is connected direct to the bias adjustment pot (the set bias control)?

Lawrence.

[barrymagrec]

That`s a standard meter rectifier - it has no adjustment.

Is the 100K resistor you mention just the series R for the meter in bias mode - not actually in the bias circuit to the head?

[DMcMahon]

Originally Posted by cdm1christopher

Yeah it is but the pot is supposed to be linked to a variable resistor in circuit under chassis and it's not.

I have no experience of the Vortexion hardware but the CBL 5 schematic shows the Set Bias to be a 25kOhm pot with one end connecting through to one connection at the erase head. A pot (potentiometer) is a variable resistor, sounds like from your description you are maybe seeing a difference between a pot and and a variable resistor ?

Not clear where the 100k comes into it, could it be a replacement for the 82k that is shown on the schematic connecting to the same end of the Set Bias pot as above and other end connecting to the Sig/Bias switch ?

David

[Luxman1050]

I'll have another look. I have the cbl5 but it differs to spec on this one. There is on a schematic forgot which one but that has a 10k variable resistor not a pot. Problem is I have 4 schematics and they all differ. Not the actual vortexion one. There all for the Ferrograph.
Yes but underneath the rectifier is a screw which is slightly been undone and just sits on back of meter freely not secured only by the wires. So what would that screw be for? And should the screw be undone? Or fully tightened? Not seen a screw on a bridge rectifier before.

[DMcMahon]

I still do not understand your reference to the variable resistor not being a pot. By pot do you mean a metal enclosed chassis mounted pot as opposed to a PCB skeleton/open pre-set type of pot (both being variable resistors).

David

[DMcMahon]

Originally Posted by cdm1christopher

Yes but underneath the rectifier is a screw which is slightly been undone and just sits on back of meter freely not secured only by the wires. So what would that screw be for? And should the screw be undone? Or fully tightened? Not seen a screw on a bridge rectifier before.

Struggling to visualize this screw can you get a photo showing it please.

[Luxman1050]

Wright oh deary me the screw now looking at it is obviously to secure it to that paxolin board see pic but it's been undone for some reason by looks of it. So initially I thought it was an adjustment screw. There is also a picture of the bias pot. When i say variable resistor I'm thinking along the lines of a resistor with a metal plate along it's length whereby an attachment can be moved back and forth to increase or decrease the ohm rating so 500k variable from say 0-500k and set it anywhere along its path to the correct ohmage to give you the voltage/current needed to adjust the bias as opposed to the fixed resistor type which you would have to use formula to get the correct ohmage resistor. So thats what I mean by a variable resistor and if you look on schematic the 10k shows it as being variable. But mine has a fixed 100k in there. The last picture shows bias readings for the two speeds. Now when I turn the bias pot not a variable resistor the type I'm on about it will only go to 50 on the signal meter but should wind right over to 500. Therefore you should be able to set it to the 140 mark.
Hope that makes things a bit clearer.

[BillDWVA]

Originally Posted by cdm1christopher

Yeah it is but the pot is supposed to be linked to a variable resistor in circuit under chasis and it's not. There's a 100k fixed resistor. So basically if you turn the bias dial as far as it can go it will only go to 50 on the meter not upto the full 500. Bias setting is supposed to be 150. Not 50 which is as far as it will go. So something along circuit needs tunning. On back of meter looks like an adjustable bridge rectifier as it has the 4 terminals with a screw underneath it.

A low bias value may be caused by a low output from the oscillator. A couple of things to check..
1) Is a Brimar 12BH7 fitted? Sometimes an ECC85 or similar might have been exchanged that has a lower gain.
2) Check the values of the resistors in the circuit as they may have gone ‘high’ leading to a lower output. Ringed in the attached.

The meter rectifier rarely gives problems and if the meter performs OK when playing and the meter switched to ‘signal’ then one can safely assume it’s ok.

An additional bit of information: On my various Vortexions it is not possible to get a bias reading on the meter of more than about 200-220 with the pot fully clockwise.

Hope this helps.

Bill

[Luxman1050]

What I forgot to add looking at picture is the switch to the left is for either switching over to set bias then back for signal.

[Luxman1050]

Cheers Bill no the brimar is in there. I think it is a resistor I had to put in a new 100k as the other had dropped to 70k. Plus the resistor between the switch and bias pot probably need changing. Couple others also needed changing gone high or low. So I'll get it all out again and check them all. Pain!!!!

[DMcMahon]

Originally Posted by cdm1christopher

Wright oh deary me the screw now looking at it is obviously to secure it to that paxolin board see pic but it's been undone for some reason by looks of it. So initially I thought it was an adjustment screw. There is also a picture of the bias pot. When i say variable resistor I'm thinking along the lines of a resistor with a metal plate along it's length whereby an attachment can be moved back and forth to increase or decrease the ohm rating so 500k variable from say 0-500k and set it anywhere along its path to the correct ohmage to give you the voltage/current needed to adjust the bias as opposed to the fixed resistor type which you would have to use formula to get the correct ohmage resistor. So thats what I mean by a variable resistor and if you look on schematic the 10k shows it as being variable. But mine has a fixed 100k in there. The last picture shows bias readings for the two speeds. Now when I turn the bias pot not a variable resistor the type I'm on about it will only go to 50 on the signal meter but should wind right over to 500. Therefore you should be able to set it to the 140 mark.
Hope that makes things a bit clearer.

A little clearer, so the adjustable screw on the bridge rectifier was a red herring.

I think now your description of a variable resistor is a "slider control" which is still a potentiometer (pot) but has straight/linear mechanical adjustment as opposed to rotational , but both versions are equally variable resistors.

Where on the schematic (which one) are you seeing the 10k variable resistor.

I know the full scale reading on the meter is 500 but how do you know that it should be possible to adjust the bias as high as 500 ?

David

[BillDWVA]

Originally Posted by cdm1christopher

Wright oh deary me the screw now looking at it is obviously to secure it to that paxolin board see pic but it's been undone for some reason by looks of it. So initially I thought it was an adjustment screw. There is also a picture of the bias pot. When i say variable resistor I'm thinking along the lines of a resistor with a metal plate along it's length whereby an attachment can be moved back and forth to increase or decrease the ohm rating so 500k variable from say 0-500k and set it anywhere along its path to the correct ohmage to give you the voltage/current needed to adjust the bias as opposed to the fixed resistor type which you would have to use formula to get the correct ohmage resistor. So thats what I mean by a variable resistor and if you look on schematic the 10k shows it as being variable. But mine has a fixed 100k in there. The last picture shows bias readings for the two speeds. Now when I turn the bias pot not a variable resistor the type I'm on about it will only go to 50 on the signal meter but should wind right over to 500. Therefore you should be able to set it to the 140 mark.
Hope that makes things a bit clearer.

Your photo of the settings shows bias recommendations of 120 at 3.75 and 140 at 7.5 which you’d set before recording with the meter switch set to ‘bias’.

The other figure ‘Peak Signal’ is the maximum recommended record signal value you can go to without distortion whilst recording with the meter switch set to ‘Signal’. Your WVA is generous here; on my Series 4 this value is 300.

Bill

[BillDWVA]

Originally Posted by DMcMahon

A little clearer, so the adjustable screw on the bridge rectifier was a red herring.

I think now your description of a variable resistor is a "slider control" which is still a potentiometer (pot) but has straight/linear mechanical adjustment as opposed to rotational , but both versions are equally variable resistors.

Where on the schematic (which one) are you seeing the 10k variable resistor.

I know the full scale reading on the meter is 500 but how do you know that it should be possible to adjust the bias as high as 500 ?

David

Component values seem to vary with year and model but the bias pot for a Series 5 appears to be 25K Lin and the series resistor 82k. If a 100k has been fitted here then the maximum bias will be lower.

Bill

[Luxman1050]

I think as said it should be adjustable to 140 but as previously said it only goes to 50 fully turned. So I'm not saying I need 500 bias reading I need either rating which is in the photo on the case. But I think your right Bill ill drop in a lower resistor. Unfortunately that was something I did not check whilst on the bench as I did not give it much thought.
A pot to me is a pot with a knob on it for adjusting volume bass etc on schematic usually has an arrow pointing to it. So a variable resistor is different symbol on the schematic does not have an arrow pointing to it. Then you have a trimmer resistor 3 pin one usually requiring 5v feed if memory serves right again it's not called a pot its called a trimmer resistor. So think obviously people have different ways of describing what a variable resistor is. Hopefully that's cleared that up.

[DMcMahon]

All understood now.