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Author Topic: TSA15H Broken down ... repair ;-)  (Read 231 times)

typ0502

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TSA15H Broken down ... repair ;-)
« on: April 20, 2017, 04:38:45 PM »

Hello

Catastrophe, mon ampli TSA15H est en panne  >:(
A certain moments, un son "srach" apparait, durant 0.25 secondes, une fois par jour ou toutes les 2 minutes !!!
Dans certain cas, à ce moment précis, le témoin ON/OFF s'éteint !!!
 :loco

Solution panne 1:
Il s'agit d'un défaut d'approvisionnement de composants.
Le régulateur 12 Volts (U3 BA12T sur le schéma, U201 7812 sur le PCB) qui alimente le chauffage des 12AX7 est en boitier TO220F (Full plastic package) passe en protection thermique: le témoin ON/OFF s'éteint et la coupure de la tension sur les lampes du préampli provoque un bruit.
J'ai remplacé par un 7812 TO220 (avec patte métallique, pâte thermoconductrice et sans isolant). De ce fait, le radiateur est un peu plus chaud ... et le 7812 un peu plus froid ;-)

Solution panne 2:
Il s'agit d'un défaut de fabrication.
Lorsque j'effleure une lampe de l'ampli de puissance, une 6V6, le  son "srach" apparait!
Je soupçonne un défaut du socket. C'est un des fils jaune, filament, dont le contact est mauvais.
Je découpe la gaine isolante et je trouve le fil torsadé mais non soudé sur la cosse.
Je nettoie, je soude, je place une gaine

Mon TSA15H fonctionne enfin comme un neuf  :dbtu:
 
Bon travail !!!
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tonyharker

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Re: TSA15H Broken down ... repair ;-)
« Reply #1 on: April 20, 2017, 05:51:24 PM »

Can you repeat that in English please?
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Enzo

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Re: TSA15H Broken down ... repair ;-)
« Reply #2 on: April 20, 2017, 08:57:56 PM »

Ran it through google translate:

Catastrophe, my amp TSA15H is down> :(
At certain times, a "srach" sound appears, for 0.25 seconds, once a day or every 2 minutes !!!
In some cases, at this point, the ON / OFF indicator goes out!
 : Loco

Solution failure 1:
This is a component supply failure.
The 12 Volt regulator (U3 BA12T in the diagram, U201 7812 on the PCB), which powers the 12AX7 heater, is in the TO220F (Full plastic package) case, switches to thermal protection: the ON / OFF indicator turns off and the Voltage on the lamps of the preamp causes noise.
I replaced with a 7812 TO220 (with metal tab, thermally conductive paste and without insulation). Because of this, the radiator is a bit warmer ... and the 7812 a little colder ;-)

Solution 2:
This is a manufacturing defect.
When I touch a lamp of the power amp, a 6V6, the sound "srach" appears!
I suspect a socket defect. It is one of the yellow threads, filament, whose contact is bad.
I cut the insulating sheath and I find the twisted but unwelded wire on the lug.
I clean, I weld, I place a sheath

My TSA15H finally works like a new one: dbtu:
 
Good work !!!
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J M Fahey

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Re: TSA15H Broken down ... repair ;-)
« Reply #3 on: April 20, 2017, 11:26:04 PM »

Funny and sadly not unusual: one of the filament wires was wrapped around a 6V6 socket leg *and*  heatshrinked ... but never soldered  :o

What is somewhat unusual is that apparently the 7812 regulator was running too hot and being the plastic insulated back type, self-turned OFF thermally.
Weird because I don´t think Crate who are experienced builders would specify a regulator (or any power device) *too*  close to maximum rating.

Guess there is a first time for everything  xP
« Last Edit: April 20, 2017, 11:31:45 PM by J M Fahey »
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