Couple of #183 derivatives

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bepone
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Re: Couple of #183 derivatives

Post by bepone »

mounted transformers on experimental chassis..
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bepone
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Re: Couple of #183 derivatives

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Amp tested clean very very nice, drive under testing, tranformers are good! Nothing too much, normal attack, normal bass , normal treble
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Re: Couple of #183 derivatives

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i have put mixed NOS and modern , for output Philips Miniwatt brown base EL34 :P
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Re: Couple of #183 derivatives

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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 :P ) 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
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bepone
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Re: Couple of #183 derivatives

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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
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bepone
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Re: Couple of #183 derivatives

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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)
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Screenshot 2.png

Caps replaced for 22uF 500V F&T, no more problems after.
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bepone
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Re: Couple of #183 derivatives

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Stephen1966
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Re: Couple of #183 derivatives

Post by Stephen1966 »

bepone wrote: Fri May 10, 2024 6:38 am faulty caps video:
https://drive.google.com/file/d/18ELqsP ... sp=sharing
The ticking is some kind of internal arcing?
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bepone
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Re: Couple of #183 derivatives

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Stephen1966 wrote: Fri May 10, 2024 10:07 am
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 :mrgreen:
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Re: Couple of #183 derivatives

Post by Stephen1966 »

bepone wrote: Fri May 10, 2024 11:02 am
Stephen1966 wrote: Fri May 10, 2024 10:07 am
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 :mrgreen:
Well you've got at least one dud there. Have you considered using thermistors for a soft start instead of a standby switch?
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bepone
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Re: Couple of #183 derivatives

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Stephen1966 wrote: Fri May 10, 2024 11:09 am 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 :P after 45 sec
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Re: Couple of #183 derivatives

Post by beasleybodyshop »

I like to use a 220K 2W resistor in parallel with a .1uFcap across my standby switches. It helps to soften the blow of immediate and direct B+.
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Re: Couple of #183 derivatives

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beasleybodyshop wrote: Tue Jul 02, 2024 2:54 pm I like to use a 220K 2W resistor in parallel with a .1uFcap across my standby switches. It helps to soften the blow of immediate and direct B+.
I also use the .1uf cap on my standby switches. Two Rock also does the same in their amps.


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