PJCSS Problem

[induna]

I assembled and installed my PJCSS upgrade kit today, replacing the Hammond chokes I had installed previously. However, my voltage measurements are NOT good, and neither is the sound. I'm getting 37.6 volts on IA and IB with new batteries. I have -.6 volts on A6 and -1 volts on B6, and 136mV on A5 and 65mV on B5. It sounds, ad you can imagine, terrible -- weak and distorted. I have triple checked my work including the polarity of the diodes and tramsistors, checked all the solder the joints -- even that really tough one at T3, and I can't find any mistakes. It was a very simple assembly process, or so I thought.

I would appreciates some suggestions on where to go from here.

BTW there is an error in the manual on page 15 where it says to locate and remove the 4.02K Ohm resistors from pin 7 of each tube socket. It should read pin 6 of each tube socket.

[Paul Joppa]

Voltages at OA, OB, bA, and bB?

[induna]

Voltages at OA, OB, bA, and bB?

OA -.7, OB -1 The difference between OA and A6 during the same measurement session is .01, and between OB and B6 is 0.

Ba and Bb are both 0

[induna]

I have now checked my work over again and I'm pretty convinced that I assembled and installed the PC board according to the instructions. I have continuity between all the connections between the board and the amp itself and all along the ground plane. All of the components on the board are installed in the right place and oriented according to the instructions, where applicable. I guess if there are no more ideas on how to identify the problem I'm having, I'm going to go ahead and pull the mod and put the chokes back in.

Thanks.

[Paul Joppa]

Two possibilities occur to me:

1) R2 is not bringing current from ground to the base of the transistor - bad solder joint, wrong resistor, or broken resistor? Measure resistance from bA to the lead of the transistor closest to IA, and similarly bB to pin close to IB to check.

2) Transistor might be inserted backwards. This is easy to confuse, since the MJE350 has the metal on the opposite side of the MJE5731A. The metal side of the MJE350 should face the outside of the board. The transistor is labeled though the print is incredibly tiny - it's probably good to read it anyhow and confirm it's the right part.

If that does not identify the problem, measure voltage at each of the three transistor leads and we'll look at that.

[Doc B.]

Looks like some kits were polluted with 470K ohm resistors when they should have received 470 ohm resistors. The 470 ohm resistor should have a light blue body and yellow, violet (very dark, looks deep blue), black, black, brown stripes. Apparently some customers received light brown 470Kohm Dale resistors marked 4703, by mistake. Others may possibly have received light blue 470K ohm resistors marked yellow, violet, black, orange, brown - though we haven't heard of anyone getting that resistor by mistake. Contact Jo at [email protected] if you need replacements.

I think we have made this "K or no K" resistor value screw up at some point on every kit we've ever released. At least we are consistent.

[induna]

Looks like some kits were polluted with 470K ohm resistors when they should have received 470 ohm resistors. The 470 ohm resistor should have a light blue body and yellow, violet (very dark, looks deep blue), black, black, brown stripes. Apparently some customers received light brown 470Kohm Dale resistors marked 4703, by mistake. Others may possibly have received light blue 470K ohm resistors marked yellow, violet, black, orange, brown - though we haven't heard of anyone getting that resistor by mistake. Contact Jo at [email protected] if you need replacements.

I think we have made this "K or no K" resistor value screw up at some point on every kit we've ever released. At least we are consistent.

Doc,  You nailed it. I have small blue 470k Ohm resistors (yellow, violet black, orange, brown) installed.

Thanks for your help. I'll send Jo an email.

[Doc B.]

Looks like there is no need to email Jo. Eileen is at the post office as I type this, sending a pair of 470 ohm resistors to everyone who has received a PJCCS kit so far.

[Mike F1]

What great customer service!!!

Accidents do happen. I'm sure some people already do this but a good tip that my Electronics Prof always suggested was to decode the color bars then use a multimeter to measure/confirm the resistance.
In the Lab many students would be careless (or like to play pranks) and not sort the resistors back in the right bins! UGH!

This is a habit that I still do and is something everyone should do to avoid some aggravation trying to trouble shoot something.

Just a thought of the day.

Mike

[Grainger49]

Mike,

I can't read the color codes very well.  I know the colors by heart but just can't see those small bands.  So I always measure.  Regardless of what it says on the outside a good meter will let you know what you have in hand.

[Len]

Mike,

I can't read the color codes very well.  I know the colors by heart but just can't see those small bands.  So I always measure.  Regardless of what it says on the outside a good meter will let you know what you have in hand.

I agree. I always measure resistors when doing construction right before attaching them.

First of all, even with resistors that have their values stamped on them, they sometimes do get labeled incorrectly. Also, all resistors have tolerances, and I like to write down what I measure on the schematic, so I am not working with theoretical values when troubleshooting. If I have a resistor string in each channel, I like to select them so that final values are as close to equal as possible on each channel.

As far as trusting resistor band math, I think that's great for showing off. I would never trust an expensive piece of equipment to such mental gymnastics. You can look at them backwards, four and five band get me all mixed up but, worst of all, the colors are not that easily identifiable to me any more. At least in new production resistors.

I only use band identification when searching my parts drawer for a certain value.

[Grainger49]

  .  .  .   four and five band get me all mixed up but, worst of all, the colors are not that easily identifiable to me any more. At least in new production resistors.

I only use band identification when searching my parts drawer for a certain value.

I thought it was only me.  Glad to see I have company.

One poster on the old board said he measured resistance from each component lead to the terminal or whatever he was soldering to after each component installation.  He had never had a bad solder joint.  Tedious but he didn't have to ever go back and troubleshoot his work. 

As much of a curmudgeon (set in my ways) as I have become I just might take that up with the next kit, Eros.

[induna]

Just an update...I received the new resistors today -- thanks Eileen -- and popped them in the board and installed the mod. Everything is now working very well. I haven't had time to do any critical listening yet, but my Quickie is now absolutely silent again. I could not avoid picking up some buzz with the chokes installed.

Thanks for the easy, fun, and productive mod.

[Paul Joppa]

... Everything is now working very well....I could not avoid picking up some buzz with the chokes installed.

Glad that it is working now - it's very frustrating when something doesn't work and you can't figure out why! Thanks for the update.

And thanks for the note about buzz - this is the first report I recall of this potential problem; it's good to know in case someone else runs into it.

[Dr. Toobz]

I'll be interested in your observations of the PJCSS compared to the Hammonds, once you get a chance. I've noticed a bit of buzz myself, now that I've "promoted" the Quickie to pre-amp status and placed it between the Seduction/DAC and S.E.X. amp (these product names really are hilarious, by the way....). If the CSS loading is as good or better than the chokes and doesn't have the inherit ability to pick up RF or AC line noise (as the chokes do), they sound like a winner.