Noob needs help with z5600a II mic repair

[Adam Frandsen]

Just some pics from inside the psu

 

[Adam Frandsen]

Now mine has a 100J in C1, the z5600 clearly states 1000pf (so a 102), and now it very much could be thar that on the z5600a II, schematic no? But, the mic in the picture from online has the 100j too… mine could have been repaired using that photo though… just need confirmation the 100j is right.

 

[Khron]

C1 being the capacitor between the backplate connection, and the tube grid?

Yes, you'll probably hear quite the difference between that 10pF ("100", resulting in ~79Hz cut-off frequency for the resulting high-pass filter), and the 1nF that it's supposed to be ("102", resulting in a 0.8Hz cut-off frequency). No small wonder it sounds "thin" then...

"J" is just the tolerance, signifying +/-5%; "K" is +/-10%.

 

[Adam Frandsen]

C1 being the capacitor between the backplate connection, and the tube grid?

Yes, you'll probably hear quite the difference between that 10pF ("100", resulting in ~79Hz cut-off frequency for the resulting high-pass filter), and the 1nF that it's supposed to be ("102", resulting in a 0.8Hz cut-off frequency). No small wonder it sounds "thin" then...

"J" is just the tolerance, signifying +/-5%; "K" is +/-10%.

Yes, I knew about the J and K part, but how frustrating that there is so much wrong, especially now since I have to order from the Us, because I cannot find 1Gohm, 1Mohm, 51Mohm resistors here, they don’t even have 9.1k or 1/2 watt ones at the electronic store, let alone good quality caps (104j, 103j and 223 they have)

 

[RoadrunnerOZ]

C1 being the capacitor between the backplate connection, and the tube grid?

Yes, you'll probably hear quite the difference between that 10pF ("100", resulting in ~79Hz cut-off frequency for the resulting high-pass filter), and the 1nF that it's supposed to be ("102", resulting in a 0.8Hz cut-off frequency). No small wonder it sounds "thin" then...

"J" is just the tolerance, signifying +/-5%; "K" is +/-10%.

If you’re talking about the pale green cap it has 630V 1n0 J written on it - the n looks like a 0 with no bottom so it’s not 100 J - if you look at the one further in it has 220n written on it with the same lower case n.

 

[Adam Frandsen]

If you’re talking about the pale green cap it has 630V 1n0 J written on it - the n looks like a 0 with no bottom so it’s not 100 J - if you look at the one further in it has 220n written on it with the same lower case n.

Wonderful, again you save the day. Too many new variables to keep track of.

 

[Adam Frandsen]

C1 being the capacitor between the backplate connection, and the tube grid?

Yes, you'll probably hear quite the difference between that 10pF ("100", resulting in ~79Hz cut-off frequency for the resulting high-pass filter), and the 1nF that it's supposed to be ("102", resulting in a 0.8Hz cut-off frequency). No small wonder it sounds "thin" then...

"J" is just the tolerance, signifying +/-5%; "K" is +/-10%.

Sorry for wasting your time on this one, I saw it wrong

 

[RoadrunnerOZ]

High value resistors you’ll get online Element 14 have over 1500 0.75W 1GΩ 1% resistors in stock - be careful what you order, those high value resistors are all usually 1% tolerance.

https://au.element14.com/ohmite/mox-400231007fe/res-1g-1-750mw-axial-thick-film/dp/2664959

 

[Adam Frandsen]

High value resistors you’ll get online Element 14 have over 1500 0.75W 1GΩ 1% resistors in stock - be careful what you order, those high value resistors are all usually 1% tolerance.

https://au.element14.com/ohmite/mox-400231007fe/res-1g-1-750mw-axial-thick-film/dp/2664959

This one should work, yes: https://www.digikey.tw/en/products/detail/ohmite/SM102031007FE/4300996

 

[RoadrunnerOZ]

Also your multimeter probably won’t read those high values if you want to test the values of those high ones (I think you said yours reads up to 20 MΩ ) unless you have an “nS” reading function on your meter (nS is nanoSiemens reading conductance from which it is easy to calculate resistance - my meter reads up to 2G on the standard resistance range however)
I have repaired many tube mics - the C12 I posted the board pics of, had a few of the high value resistors drifted in value affecting the tube performance - the 3GΩ was fine in that but because it was above the range of my meter, I had to measure that out of circuit by tacking a resistor in series with it, applying 24V DC across the two and measuring the voltage across the lower value resistor using the high impedance low mV range on my meter and calculating the actual value of the 1GΩ resistor. Bit of a runaround but this was a complete refurbishment.

 

[RoadrunnerOZ]

This one should work, yes: https://www.digikey.tw/en/products/detail/ohmite/SM102031007FE/4300996

Perfect

 

[RoadrunnerOZ]

I have yet to change any resistors, as my local electronics store was out of most for some reason yesterday. I could buy two 150k@2watt, which I did, and I soldered them together in a V/triangle shape, and they measure right, but they can barely fit haha, haven't soldered them on yet.

And yes, they are all 270k those three in mine, which is wrong. And one measures completely wrong too,

You need to measure them out of circuit. If using two resistors in series the wattage required is halved, as only half the voltage appears across each resistor.

 

[Khron]

This one should work, yes: https://www.digikey.tw/en/products/detail/ohmite/SM102031007FE/4300996

Why do you need to replace ALL the resistors though?

Pro tip: Mouser carries the TE Connectivity RGP0207 series of high-value resistors, for well under $1/pc. And they're also not as humongous as the stuff from Digikey, since they don't need to be dissipating any significant power.

 

[Adam Frandsen]

You need to measure them out of circuit. If using two resistors in series the wattage required is halved, as only half the voltage appears across each resistor.

They only had 2watt, thats why I did it like that… now I am ordering from US, I will get the right size

 

[RoadrunnerOZ]

Why do you need to replace ALL the resistors though?

Pro tip: Mouser carries the TE Connectivity RGP0207 series of high-value resistors, for well under $1/pc. And they're also not as humongous as the stuff from Digikey, since they don't need to be dissipating any significant power.

Agree with you there - just had a search through and Digikey are limited in what they have - also most of them are bulk pack or out of stock. I use Mouser as they’re quick as well. For me if RS Components or Element 14 don’t have local stock as both are near me Mouser is my next choice. 1/2W should be more than enough for R3

 

[Adam Frandsen]

Why do you need to replace ALL the resistors though?

Pro tip: Mouser carries the TE Connectivity RGP0207 series of high-value resistors, for well under $1/pc. And they're also not as humongous as the stuff from Digikey, since they don't need to be dissipating any significant power.

Why do you need to replace ALL the resistors though?

Pro tip: Mouser carries the TE Connectivity RGP0207 series of high-value resistors, for well under $1/pc. And they're also not as humongous as the stuff from Digikey, since they don't need to be dissipating any significant power.

Just because it would make me feel better. Important question though, R4 seems to be 1K in the z5600a schematic and maybe 3.9K in the blurred z5600a II schematic, is 1K the right value?

 

[Adam Frandsen]

Also your multimeter probably won’t read those high values if you want to test the values of those high ones (I think you said yours reads up to 20 MΩ ) unless you have an “nS” reading function on your meter (nS is nanoSiemens reading conductance from which it is easy to calculate resistance - my meter reads up to 2G on the standard resistance range however)
I have repaired many tube mics - the C12 I posted the board pics of, had a few of the high value resistors drifted in value affecting the tube performance - the 3GΩ was fine in that but because it was above the range of my meter, I had to measure that out of circuit by tacking a resistor in series with it, applying 24V DC across the two and measuring the voltage across the lower value resistor using the high impedance low mV range on my meter and calculating the actual value of the 1GΩ resistor. Bit of a runaround but this was a complete refurbishment.

I got a new one that goes up to 200MΩ today and bought one for capacitors as well, the 100uF are down to 83 (don’t know if it is okay, but will change anyhow), the 1uF‘s are at 0.903 ca. - I haven’t had time to measure them all yet.

 

[Adam Frandsen]

Also an important question, R9 and R10 are not part of the z5600a with readable schematic, in the blurred one they look like 1M, but I am not 100% sure now, becasue the other mic with same pcb from online has 3 equal values there as well as mine (270K)… so, what is right

 

[Adam Frandsen]

Agree with you there - just had a search through and Digikey are limited in what they have - also most of them are bulk pack or out of stock. I use Mouser as they’re quick as well. For me if RS Components or Element 14 don’t have local stock as both are near me Mouser is my next choice. 1/2W should be more than enough for R3

All three have Taiwanese websites, but Mouser and Element 14 seem to maybe have physical addresses in Taiwan too, gonna call tomorrow and find out if there is a local warehouse.

 

[RoadrunnerOZ]

And yes, they are all 270k those three in mine, which is wrong. And one measures completely wrong too, 1.1kohm.

Check the one that reads 1.1KΩ OUT of circuit - no good trying to get a reading while it’s in circuit - then you can check the circuit as well - you will get a rising resistance reading from R6 top position as your meter is charging the filter capacitor via the filter switch and output transformer primary. Depending on switch position the reading and drift time will be different. If you’re getting a solid 1.1KΩ reading try removing the tube, if it still remains, change the filter switch position and see what you get.