Couple of #183 derivatives

[bepone]

mounted transformers on experimental chassis..

IMG_20240429_190011.jpg

[bepone]

Amp tested clean very very nice, drive under testing, tranformers are good! Nothing too much, normal attack, normal bass , normal treble

[bepone]

i have put mixed NOS and modern , for output Philips Miniwatt brown base EL34

IMG_20240430_112609.jpg

[bepone]

last 2 days update on the OD sound and tweaks..while clean is correct, OD wasnt so..

i have found OD sound too fuzzy for my taste, not amusing in any way... on the lower register.. tweak to cure that - both OD potentiometers changed from 100k to 250k..(actually they are like that in 183 schematic, not 100k, and i was tryin to keep 183 topology but have drifted a lot somewhere in testing ) and in the same time i have used chance to change all 4 cathode capacitors V1+V2, from regular blue mallory 4u7 to gold color Roederstein bipolar EBT 4u7 (all measuring 5.05uF-5.07uF)..

all together.. OD changed to great

IMG_20240502_101550__01.jpg

[bepone]

For the past weekend we had some festival dedicated to vinyl and tubes, where was amp played.. i took nude and rude version without box.. Very nice experience.. maybe little bit too fatty/creamy sound with 1x12" Alnico Cream.. room and people damped the heights so better in the start to have more middle in the sound

here are some clips,
https://drive.google.com/file/d/1QVgXNH ... sp=sharing

https://drive.google.com/file/d/1N4gyJ9 ... sp=sharing

[bepone]

Here is something what happened after in the amp.. failure on 450V elcos in the preamp section (they were new Kemet - Long life - ex Rifa) ?

Very strange, i didnt measure wall voltage before.. maybe little bit over 230? Looks like caps took surge voltage during cold start (power and standby switch probably started together - cca 460-470V maybe was on them).

And this is why WE NEED STANDBY SWITCH because nowadays those veeeery smart guys on the net telling that standby switch no needed

Screenshots on voltage on the elco (dropping from 400-200V - shorting or arcing internaly)

Screenshot 1.png

Screenshot 2.png

Caps replaced for 22uF 500V F&T, no more problems after.

[bepone]

faulty caps video:
https://drive.google.com/file/d/18ELqsP ... sp=sharing

[Stephen1966]

faulty caps video:
https://drive.google.com/file/d/18ELqsP ... sp=sharing

The ticking is some kind of internal arcing?

[bepone]

The ticking is some kind of internal arcing?

Yes, and the voltage drops are there too in the same time.. on variac if i lower the input voltage, then in one moment is ok situation, but on nominal looks like is going to the white smoke.

Chasing the ghost

[Stephen1966]

The ticking is some kind of internal arcing?

Yes, and the voltage drops are there too in the same time.. on variac if i lower the input voltage, then in one moment is ok situation, but on nominal looks like is going to the white smoke.

Chasing the ghost

Well you've got at least one dud there. Have you considered using thermistors for a soft start instead of a standby switch?

[bepone]

Well you've got at least one dud there. Have you considered using thermistors for a soft start instead of a standby switch?

not really , because you need to hold high voltage at least 20-30 seconds and if not.. all of the Ub line caps will be on max voltage .. You need something like 500k.

So or Automatic delay (unnecesarry electronic circuits) or manual triggering STBY switch .. i prefer the best method - manual after 45 sec