Wad step ups

[Bizzie]

I fired up my phonoII today to find that I only had the left channel working and a low hum from the right after swapping cables around isolated it to the right channel.

As some of you may remember from the wad bb I have fitted my phonoII with switchinge between MM and MC cartridges so when it worked perfectly with a MM cartridge I started to investigate the wiring and switching first and could find no problem as I don't have the time to unsolder anything I have checked the step up windings and both measure the same onthe input @ 1.4R the out put is a different matter the secondries measure 0.6R left channel(working channel) and 134.5R on the right channel.

It looks like there is a problem with the output coils although I would need to completely disconnect them to be sure, if the coils have developed a fault would it be just bad luck or could some other problem have caused the fault to develop.

[John Caswell]

Hi Bizzie,
Oh dear, on the face of it you have a u/s step up tx, but you need to disconnect them both to compare, rather than measure them in circuit.
I am surpised that the ratio of the working one is 1.4R to .6R as it is a step up device so I would expect a higher R on the secondary.

John aka Dr John

[Bizzie]

Yes I thought that should be the case but I haven't had the time to desolder them today but that must be because they are in curuit, but because there is a big difference I would think it shouldn't be too hard to trace if it doesn't turn out to be the stepups.

If it is the step ups I just hope that it was faulty and not caused by something else.

I have noticed that the right channel was quieter lately but thought that one of the valves may have been on its way out but since its OK set to MM then thats not the case

[Paul Barker]

The .6r one is either shorted by the circuit or internally shorted, since you haven't disconnected it I would expect the dead short to be in the circuit.

Tell me when you connect your meter probes together do they also read .6 r?

You need a low ohm meter for that level.

I bet the short is in your switch. Hard wire the option you are using at the moment. Who can be bothered changing cartridges all the time?

[John Caswell]

Paul,
You are not reading the information given, the 0.6R reading is on the tx side that is working.
Maybe you cannot be bothered changing cartridges but perhaps Bizzie has two turntables or two pickup arms.
Don't just bet on things, try leading the person to the correct way to find the fault

John aka Dr John

[Paul Barker]

Well I'll bet on the faulty channel being the 0.6r one, may be a mistake in his assessment of the situation.

As for a switch from mm to mc, hope it's a good one.

As for taking bets on what is wrong, the persons' statements don't always ring true and my chrystal ball needs a clean so I have a stab at what I think might be happening.

[Bizzie]

Today I found the time to take another look and after desoldering the right TX found that it was OK out of the circuit, the left one was also checked out of circuit and is Ok too.

After checking everything over I couldn't find any problem so decided to re-assemble and found that it now measures the same both sides in circuit, so I decided it must have been a dry joint somewhere.

I put the PhonoII back in my system and tried with a MM cart first with no problem, next the Denon 103 and OL1 were connected(yes I do have more than one arm on my deck) with the result that I had no right channel again. Off came the arm and cartridge and when I checked it with my meter for continuity found that there's no ground on the left channel, a visual examination revealed that the ground wire has snapped where it goes into the arm (**** origin live wiring) so it looks like I have another repair to do.

I think that I may have pulled the wires when refitting the Denon when I added a weight to the headshell but there was definately some thing wrong with the wiring inside the PhonoII, they say things come in three's so I'm wondering whats coming next.

[John Caswell]

Hi Bizzie,
Well done, Sod's law is alive and well I am glad to hear. not goind to comment on things coming in threes as they seem to come perpetually for me!
If you have to attack the arm wiring it might be worth fitting the Incognito rewire assuming it is an RB250/300 type arm.

Regards

John aka Dr john

[Paul Barker]

Out of interest what was the dc resistance of the secondary's?

[Bizzie]

Originally Posted by Paul Barker

Out of interest what was the dc resistance of the secondary's?

It was 131R so you may have been right about me getting the readings mixed up.

I will not spend £175 on some wire for the Incognito kit when all it made from is cardas wire that can be had for about 80p a foot and woven copper sleaving at 30p a foot from Michael Percy, trouble is i've been tring to place an order with them and keep getting emails saying they're canceling the back log of orders and if its important please try a re-order very frustrating.

Has anyone else managed to get an order in with Michael Percy recently this is the first time i've tried to order from them and I'm getting fed up with resending the order only to have my email binned again.