Rocket Voltage Problem Fixed - Distortion Problem

[strato17]

This is my second amp build, the first of which was an Express, which went very well.

I am getting some over-voltage problems with my Rocket build.

Actual Expected
Mains
120.8 120.0V

Secondaries
511 506

B+1
304.8 290

B+2
295.2 279

B+3
250.4 212

B+4
236.3 187

B+5
231 183

It appears that most of the voltage problems occur after the choke is introduced(B+3 and beyond). It appears that all the correct resistor and cap values have been used.

However, I noticed that the Taylor Rocket schematic lists a 15H 25 mA choke, while Ron's BOM lists a 15H 75 mA choke. I used a 75 mA. Which is correct, 75 mA or 25 mA, and could this be the source of my voltage problems?

If the choke is not the culprit, any ideas of where I should be looking?

[M Fowler]

The correct choke is what Ron has listed the Hammond 158L 15H, 75mA, 411 ohms.

Which PT dd you use?

[strato17]

The PT is a HTS-5199.

My choke is an Edcor with:
15H 75mA, 347 Ohms

[M Fowler]

The choke is fine.

Your using the 260v tap to get 511v secondary. The B4 and B5 are the ones that are way too high

Your voltages are up compared to the compiled list. Are you using 9k1 resistors on the dropping string?

The PT uses 5v/3A you could use a 5u4 rectifer tube to reduce the overall voltages, which is less efficient then the 5AR4/GZ34.

If your resistors are correct 9k1 you can increase their value.

[strato17]

The choke is fine.

Your using the 260v tap to get 511v secondary. The B4 and B5 are the ones that are way too high

Your voltages are up compared to the compiled list. Are you using 9k1 resistors on the dropping string?

The PT uses 5v/3A you could use a 5u4 rectifer tube to reduce the overall voltages, which is less efficient then the 5AR4/GZ34.

If your resistors are correct 9k1 you can increase their value.

They are indeed 9k1's. I added two 9k1 resistors to equal 4 9K1's between B+2 and B+3.

I now get
ON Expected
Mains: 122.3 120.0V
Secondaries: 519 506
B+1: 309 290
B+2: 299 279
B+3: 219 212
B+4: 207 187
B+5: 202 183

The numbers look a little better, however, the amp still farts out.

When a note is played, it briefly distorts then the volume drops significantly. Any other ideas? I'm at a loss.

[fishy]

Have you done a full voltage chart yet? That would be the first step for me.
Some pics might prove helpful to some of the mre knowledgable guys.

I would be hesistant changing dropping string values without understanding the farting out issue.

[strato17]

It's not the cleanest build, but here are some pics and a voltage chart....

[IMG:800:600]http://img.photobucket.com/albums/v238/ ... hoto32.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v238/ ... hoto34.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v238/ ... hoto35.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v238/ ... hoto31.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v238/ ... hoto30.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v238/ ... hoto29.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v238/ ... hoto28.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v238/ ... hoto27.jpg[/img]

[IMG:800:600]http://img.photobucket.com/albums/v238/ ... hoto26.jpg[/img]

[fishy]

Is it fair to assume the tubes are known good at this point and the component values have been verified?

Some of the connections look like they might benefit from reflowing. If they are not the issue it will likely improve the reliability long term.
Easy and relatively quick.

[strato17]

The resistor values seem fine. I do not have a meter that can check capacitance so I suppose it is possible there is a bad cap? I will reflow the solder points and try some tube swapping. Thanks for the help.

Any other ideas are welcome.

Thanks!

[fishy]

You might have looked here already but just in case you have not it might be worth a look.....

http://www.geofex.com/ampdbug/ampdebug.htm

[M Fowler]

I am getting some over-voltage problems with my Rocket build.

Nice looking build

I haven't heard what problems you are having and it appears to me that your only concerned about voltage not being in line with the amp you choose to compare yours with.

Your running 122v at the wall plate so your total voltage is going to be higher.

[rooster]

strato - Um, the input jack? You seem to have the load resister hooked up incorrectly. It needs to go to permanent ground on the jack, right? Prolly a simple mistake.

Oh, it also looks like something other than a 1meg?

[Structo]

Good eye!

That does look suspect.

Also, I would ground that jack to the buss wire, but I do understand you guys like to copy Ken's design so it's probably alright there.

[M Fowler]

I think its a solder issue, when the strings are hit causing large in rush and caps aren't delivering voltage.

Make sure each tube is seating well also. Look at the PI tube socket well.

Did you change the 1m resistor as shown goes from tip of jack to ground tip then back to middle switch. Doesn't reguire extra ground wire.

[strato17]

Well, I failed to connect R7 to ground(as seen above). Needless to say, that fixed the voltage problems. However, I am now experiencing ALOT of overdrive in the amp. I wouldn't say it's horrible sounding overdrive, but it's not desirable either. I have to run the volume at 8o'clock or less to get a remotely clean tone.

I am out of town, but when I get back, I will investigate. What is the desirable cathode current for this amp? Also, any other ideas of what to check?