Teezer 15v build question

[stevebryson]

Hi Wigglers! I'm building a teezer from the Bridechamber kit, which has the parts for the Dave Brown 15V modification. Dave's mods includes the line "Change R119 from 22K to 30K". The thing is that the Teezer BOM and schematic say that R119 is 12K. So there's a misprint somewhere, and where probably matters.

Should Dave's mod read
"Change R119 from 12K to 30K"
or
"Change R??? from 22K to 30K" where R??? is one of the 5 22K resistors (R24, R25, R123, R131, R133) and if so, which one?

Thanks!

[sduck]

According to the docs I have R119 is supposed to be 22K. Mine are pretty old though, but I doubt they've changed - perhaps Ian can be contacted, or maybe he'll see this? There are no 12k resistors in my BOM.

[stevebryson]

According to the docs I have R119 is supposed to be 22K. Mine are pretty old though, but I doubt they've changed - perhaps Ian can be contacted, or maybe he'll see this? There are no 12k resistors in my BOM.

Thanks sduck - here's an excerpt from teezer_board_a_doc.pdf. Does your doc have a different name?

I suppose since R119 is connected to power that must be the one to change. So did you use 30K and it works fine? R119 is hidden in the photo of your teezer board.

[frijitz]

Sorry for the confusion. There was a design change at some point, to allow a softer sync. The modified value of R119 is 12k. With this value there is no sync action until the control is turned up a bit. I was trying to avoid this dead zone originally -- up until I realized that very soft sync with the master allows tracking over a wide range with minimal waveform distortion. (See the thread at e-mus.). For 15V supplies the best value would be 18k.

I would be glad to supply the corrected docs to anyone who needs them.

There is another error on the docs. R132 and R133 should be reversed. Probably doesn't hurt operation, though, just gives a little less margin of error designwise.

Ian

[stevebryson]

Thanks Ian! I'll send a note to Scott. I guess we should make sure Dave Brown sees this.

And just to make sure we're talking about the same docs, you mean R133 should be 27K and R132 should be 22K, yes?

[sduck]

Glad Ian came and filled in the blanks here.

[davebr]

Thanks Ian! I'll send a note to Scott. I guess we should make sure Dave Brown sees this.

And just to make sure we're talking about the same docs, you mean R133 should be 27K and R132 should be 22K, yes?

I've added notes to my web page.

Dave

[stevebryson]

Thanks, everyone. I think I got it.

One more thing: I got myself thoroughly confused about the switch wiring, and diagram links on other build threads are dead. It took me a bit to figure out. In case anyone else looks here, here is my Ian-approved solution (apparently there are other possibilities). The "AC" and "DC" refer to the position of the switch lever, in other words the labels on the panel.

[iopop]

stevebryson: Thank you for posting that image. Saved me lots of time.

Finished this bad boy today. Been in my backlog since 2011. Everything worked on first power on! Super easy build. Not sure why I waited so long to finish it.

[phisynth]

Sorry for necrobumping this thread !

I'm currently building this for +/- 15V and was wondering if there's any pros / cons doing the Dave Brown mods by changing a lot of resistor values as seen here :

http://www.dragonflyalley.com/synth/con ... O.htm#mods

instead of the one described in the build docs, by replacing the ferrite beads with 2.7 / 3.0 v zener diodes :

Addendum: Modifications for +/- 15V Power
The most convenient method of adapting this project to +/- 15 V power is to reduce the power lines to 12 V
using series Zener diodes. This may be done without board modification by replacing the six ferrite beads with
Zeners. Two different device types are used because the different sections draw different currents. The
substitutions are:
B201, B202 1N5225B, 3.0 V Zener diode
B203-B206 1N5223B, 2.7 V Zener diode
Important: use only the specified devices.

thanks in advance for your input

[emmaker]

Here are my thoughts on it.

If I were putting it into a Euro system I'd use the ferrites. If I'm putting it in an MOTM system you could go with either.

There is gettting to be a lot of digital (computer) electronics in Euro systems. These can have issues with putting high frequency signal through a system. Either on the power supply or by RFI. The ferrites might help with those issues. For MOTM systems you don't tend to have as many computers in the rack.

[deepblackjoe@gmail.com]

I dredged this one up instead of starting a new thread. I'm building a 4u teezer pcb for 15v. I started with all the resistors, including Dave Brown's subs, and got to the zeners. Mr Fritz's addendum says to swap out the six ferrites for various zeners to accommodate 15v operation, and Dave has four others to change, that seem to cover the changes the others would make, but without changing power to all chips to 12v, so if all the resistor changes have already been made, at this point I would keep the six ferrites and Only change the four per Dave's notes, is my thinking correct on this? I'm hoping someone out there knows what I mean. I should not do Ian's addendum if I'm doing Dave's (and vice versa)

[frijitz]

One or the other, not both.

Ian

[deepblackjoe@gmail.com]

Thanks for that, will go ahead and keep the ferrites. While I have your ear Ian(!), How important is the power dissipating rating in zener choice? I only ask because all on hand are the 1n4xxx type..and the higher rating I think, but maybe there are situations where less is desirable, like the 1n5xxx you specify.