Search found 241 matches

by playonit
Sun Sep 17, 2017 10:43 pm
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

The only issue now is a loud shrill sound that fades immediately after I take it off standby and a harsh gated sounding distortion when I pluck a string hard... This may be a sign of improper phasing of the NFB loop. Disconnect the feedback wire from your speaker jack. Does the sound get better? If...
by playonit
Sun Sep 17, 2017 4:57 pm
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

meter set to measure dc volts We have sound ..... As you suspected it was a missing Jumper on the 2.2k and 22k resistor.. I have traced the amp 5 times never caught it :oops: The layout when printed did not print the light gray underboard wire so I never seen or traced that all the times I went ove...
by playonit
Sun Sep 17, 2017 3:59 pm
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

I think you should concentrate on the high voltage on V4 pins 1 and 6. Until that is fixed you will not get any sound through this amp. Measure the voltage directly across the 91K and then the 82K plate resistors (meter leads directly on the leads of each resistor). If the voltage is zero or very s...
by playonit
Sun Sep 17, 2017 1:45 pm
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

Stevem wrote: Sun Sep 17, 2017 11:05 am No, not from each cap to ground, across each cap!
Measurement across the caps while strumming is 6.2vac ... What am I looking for that to tell me? Thanks Steve!
by playonit
Sat Sep 16, 2017 3:46 pm
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

The PI plates have coupling caps feeding pin 5 of the output tubes, hook your probes up the output tube side of those two caps. If I follow you correctly I put black probe to ground and red probe to output tube side of the coupling cap and I get 120vac on each cap. Strumming the guitar has no affec...
by playonit
Fri Sep 15, 2017 6:19 pm
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

Stevem wrote: Fri Sep 15, 2017 4:20 pm If you hook up a voltmeter set for AC volts across the output of the PI ( output tube side) and play thru the amp do you read voltage, like over 20 vac?
Being the electronics novice that I am. Could you be mores specific as to where I would place my probes... I really appreciate the help...
by playonit
Fri Sep 15, 2017 4:00 pm
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

Going back to where you had 491 volts on the output tube plates , this would infer that your AC input to the recto bridge was 350 volts on each leg, is this about what you have if the power tubes are yanked out? I think it's just time to plug in and play it! Besides the high voltage on the PI plate...
by playonit
Fri Sep 15, 2017 12:35 am
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

If like you have posted in your chart that the bias voltage on pin 5 of any output tube is -61 volts then that why your voltages thru the rest of the amp are so off the mark! Your output tubes are not even idling with -61 volts on pin 5 to load down the power supply! Bring that down to -42 and see ...
by playonit
Thu Sep 14, 2017 1:46 am
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

Well this one has me shaking my head.. I just once again traced the circuit thinking I had to have missed something but all appears right..I am a novice at this stuff and this is only my fourth amp build and the only one so far that has given me fits.. I don't really understand how to introduce a si...
by playonit
Wed Sep 13, 2017 10:33 pm
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

xtian wrote: Wed Sep 13, 2017 3:51 pm With amp off and caps discharged, please measure resistance from HT1 to HT3 as shown on power supply schematic.
I read 1k from HT 1 to HT 3...... From HT1 to HT2 I read 569 ohm ... what should I be looking for ?
by playonit
Wed Sep 13, 2017 2:15 pm
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

No they are not swapped... what would be good points to check voltages other than voltages at the pins and report those back? For example I get high voltage when I check each side of the 470r resistor that is from the screen/grid each side is 480vdc is that correct? Thanks for the help :D
by playonit
Wed Sep 13, 2017 12:38 am
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

Here are the Schematics and layout I worked from.. I have traced this circuit at least 4 times and all appears correct. At this point I have to believe it is possibly a bad component.. I have ordered a new 470r 100r resistor and will replace the 2w 1k as well... Is it possible for a resistor to test...
by playonit
Tue Sep 12, 2017 12:19 am
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

Do you mean the power supply dropping resistor on the board? if so, one side measures over 400vdc and the other side about a 100 volt drop at about 326vdc Double check this. You're saying you read 326v at that node--doesn't this same node feed the PI plates? Not possible, since you see 400+v on you...
by playonit
Mon Sep 11, 2017 2:09 am
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Re: Hiwatt build voltage issues

Check the HT dropping resistor between the power tube screens node and the PI node, and check the PI plate resistors. Confirm the proper value in each case and proper connections. Are you getting sound? I am getting high voltage on both sides of the 91k and 82k plate resistors over 400vdc on both s...
by playonit
Mon Sep 11, 2017 1:12 am
Forum: Vox/Hiwatt Discussion
Topic: Hiwatt build voltage issues
Replies: 35
Views: 7113

Hiwatt build voltage issues

I just finished building a dr103 using the Schematic and layout for the early 70's circuit from the Hiwatt pages. after measuring my voltages I found the plate volts on V4 (12AT7) measured 480vdc? I have changed tubes re-flowed a few joints and retraced the circuit a few times with all checking out....