Voltage problems

[guf]

Just finished my S.E.X amp. Not knowing anything about amp building I'm amazed that following instructions and soldering parts can produce sound.  I did have a few problems.

Resistance checks were with in range besides

A6  8.16
B6  1.18

Voltage had a few more issues

9 and 19    20 and 20
A1 and B1  20 and 25
A5 and B5  215 and 82
A6     9.4
C2     2.3
C5     2.5

I checked for obvious flaws and cant find anything. Thoughts or suggestions? My kit came with 2 different style of tubes but switching them did not make a difference.
thanks
guf

 

[Paul Birkeland]

Start with C2 and C5, double check the orientation of those diodes, and the connections between the diodes and the terminal strip and transformer.

Having this voltage at 2.5V will throw the rest of the circuit out of whack.  Do the tubes glow?

 

[guf]

yes they glow. and it even produces sound, good sound, just not great. it distorts at higher volume. the right channel (a side) is slightly quieter. thanks for your reply.

 

[Paul Joppa]

A6 has a resistor to ground that should be 1270 ohms, which is 1.27K ohms. There is an 8.2K resistor in the power supply, which is closer to what you measured - perhaps the resistors were swapped accidentally?

 

[guf]

A6 has a resistor to ground that should be 1270 ohms, which is 1.27K ohms. There is an 8.2K resistor in the power supply, which is closer to what you measured - perhaps the resistors were swapped accidentally?

I'm suspecting the problem is something like this. the picture shows them being identical. the 8.2 k and the 1.27 look identical? trying to figure out which is which. can i test them by placing the meter probes on each side and noting the number?

 

[randy@matrixq.com]

Yes.  You can test resistors just as you described.  Keep your body out of the circuit (do not hold the leads with your fingers) and you will get an accurate read.

I check every resistor before soldering.

 

[guf]

also i should mention i was going off the old instruction guide and the switched to the new around paged 32. could i have some earlier discrepancies causing problem switching for old to new manual?

 

[Paul Joppa]

Well, both resistors are installed at about the same time. Look at the new manual, bottom of page 33 - the resistors look very similar, and are near each other and parallel. The 8.2K resistors are installed on p.32, the 1.27K on page 33.

 

[earwaxxer]

I check every resistor before soldering.

True - measure twice - cut once. Good rule to live by.

 

[guf]

Measuring the 4 light blue resistors from the bottom of page 33, None of them measure 1.27k. I did figure out that i had 2 of the 8.2 's on the A side. I changed them and my A6 value went down to 130, closer but off  and the other values are still too.  The Amp does perform well. The right side is a bit quieter but over all it's working great. Is it possible to have voltages so off and still get good sound?

 

[Paul Birkeland]

I'd repost any voltages that don't match (recheck them all).

 

[Grainger49]

Guf,

You need only post the voltages or resistances that are greater than 15% off, plus or minus.  It will help the posters if you post your reading and the expected as well.  That keeps us from flipping back and fourth in the manual.

 

[guf]

thanks for the replies and here is the updated data that is still off

Resistance
A6   3.2       should be   1.27
A2,B2   0    should be varying      

Voltage
9 and 19     20 and 20 fluctuating  should be close to 0
A1 and B1  20 and 25 fluctuating  should be close to 0
A5     131         should be 75
A6     5                       should be 2.5
C2     2.3               should be 3.15
C5     2.5       should be 3.15

 

[guf]

Replaced a few resistors and re soldering got my resistance in range.

Some my voltage problems revolved around the 220 ohm 1/4w carbon composition resistors. I got one side good and solved the A1 to 9 problem, then overheated the B1 to 19. I'm hoping i can replace those from my local store in the morning.

Still struggling with the C2 and C5 i'm getting a reading of 2.3 instead of 3.5. i was thinking of replacing the .1 wirewound resistor. could that be a problem?

 

[Paul Birkeland]

What's the AC voltage between the power transformer terminals 4 and 5?

 

[guf]

I think i measured it right, turn on, clip terminal 4 and touch terminal 5, and set my meter on ac? 6.5

 

[Paul Birkeland]

Yes, 6.5V AC is correct.  Can you double check the capacitor orientation?  Somewhere along the way, you are losing a couple of volts from the heater circuit, and I'd be suspicious of a backwards cap or backwards diode.

 

[guf]

my replacement 220 ohm 1/4w carbon composition resistors for A1 to 9 and B1 to 19, look different than the supplied ones that came with the kit. Those voltages continue to fluctuate around 20 instead of 0. Also I still can not locate the problem around the C2,C5,A8 loosing a few watts. They appear to be installed correctly as does the capacitor for C1 to C2, and the .1ohm wirewound resistor at C2/C5. One of the 4  Schotty diodes is different than the rest, not sure if that could be a problem.
Not sure if its unsafe to have these voltages off and use the amp....AND it annoys me not to have the numbers right but it sounds as i good as i expected it to. 
I appreciate any more suggestions. thanks

 

[Paul Birkeland]

How is the one diode different from the others?

 

[guf]

How is the one diode different from the others?

the writing is horizontal instead of vertical.
is there a way to test them while they are in place?