Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Please login or register.

Login with username, password and session length
Advanced search  

News:

SSGuitar has been upgraded to SMF v2.0.14 and PHP7!

collapse
Pages: 1 [2]   Go Down

Author Topic: Newbie Help please - Hartke A25 Bass Amp combo  (Read 668 times)

Psabin8951

  • SSGuitar Apprentice
  • **
  • Chip Points: 0
  • Posts: 8
    • View Profile
Re: Newbie Help please - Hartke A25 Bass Amp combo
« Reply #15 on: June 13, 2017, 06:56:02 AM »

ok so with Q4 removed the reading was as expected so Q4 now replaced and to be sure d13,14,q2,3,5 also.
I now get a hum when a guitar is plugged in, R97 doesn't get too hot but Q8 catches fire!! It literally glows.
I'm about to give up on this one unless anyone has any final ideas for me.
Logged

phatt

  • Legendary
  • ******
  • Chip Points: 198
  • Posts: 1715
    • View Profile
Re: Newbie Help please - Hartke A25 Bass Amp combo
« Reply #16 on: June 13, 2017, 08:04:03 AM »

Sorry to hear,,, Q, Are you using a limiter? 8|

These are Direct Coupled high current circuits and obviously if the circuit is unstable you can blow transistors before a fuse even has time to get out of bed. :)
To circumvent instant destruction of all your hard work you need to limit the current and the best way to do this is with a very simple electrical trick all details to build a Light Bulb Limiter can be found on this forum.
So before you crucify anymore components you need to build a limiter which allows you to get voltage readings around the circuit to get an idea of where the problem exists. if the current tries to rise the bulb Absorbs the inrush and *Limits* voltage saving the transistors from INSTANT DESTRUCTION. :'( :'(

Light Bulb Limiter circuit and build notes at the top of this page;
https://www.ssguitar.com/index.php?board=2.0

Build that then some of the more savvy tecks can tell you where to take voltage readings and they will guide you through the process of rebuilding the circuit.
Don't give up just yet,, Phil.
Logged

Enzo

  • Legendary
  • ******
  • Chip Points: 177
  • Posts: 1632
    • View Profile
Re: Newbie Help please - Hartke A25 Bass Amp combo
« Reply #17 on: June 13, 2017, 10:57:18 AM »

And maybe we forgot, but I hope we made mention of not connecting a speaker until we know the amp is stable and not producing DC?
Logged
Pages: 1 [2]   Go Up
 

* User Controls
 
 
Welcome, Guest. Please login or register.
Did you miss your activation email?
* Recent Posts
Yamaha PC4002M blowing fuses/output transistors by phatt
[Today at 08:29:39 AM]


Noisy Princeton Reverb 65 by J M Fahey
[Today at 02:24:13 AM]


Compressor Mods by phatt
[August 19, 2017, 04:51:16 AM]


Acoustic 150 - Hat in Hand by JackSpratt
[August 18, 2017, 07:57:31 AM]


Randall RG100 G3 Plus by zadmight
[August 17, 2017, 09:18:12 AM]

* Sponsors