|
Home | Forums | Rules | Articles | diyAudio Store | Blogs | Gallery | Wiki | Register | Donations | FAQ | Calendar | Search | Today's Posts | Mark Forums Read | Search |
Solid State Talk all about solid state amplification. |
|
Please consider donating to help us continue to serve you.
Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving |
![]() |
|
Thread Tools | Search this Thread |
![]() |
#31 |
diyAudio Member
|
![]()
see attached
|
![]() |
![]() |
#32 |
diyAudio Member
Join Date: Apr 2010
Location: Coffs Harbour, NSW
|
On Semi's KSC3503/KSA1381 have been the go-to CRT driver transistors here for many years. If SMD is OK, BF720-722 are Nexperia and Infineon's SOT223 versions of the original Philips and Siemens BF469/470. Their wide collector tabs provide for some essential cooling but perhaps not enough for ETI477, where the VAS normally runs very hot.
__________________
If only I had listened.... |
![]() |
![]() |
#33 | |
diyAudio Member
Join Date: Jun 2013
Location: Perth
|
Quote:
Thanks for the info Ian. Would these be direct "drop in" replacements for the BF's ?? Also, I notice that the 2SC3505 and the KSC3505 are noted on the data sheets as the same. Is this correct or is there actually a difference ?? |
|
![]() |
![]() |
#34 |
diyAudio Member
Join Date: Apr 2005
Location: Buskerud
|
Tran, not re.
Snigger. R |
![]() |
![]() |
#35 |
diyAudio Member
Join Date: Jun 2013
Location: Perth
|
Thanks Arthur, I can see a few component changes in your schematic. A couple of quick questions please. The position of R16 and C5 are reversed and the voltage of C5 reduced from 25v to 16v in your schematic. Is there a reason for this ? C6 (10pF) has been increased to 12pF in your circuit. (NFB) Cap C14 on the base/collector of Q6 is increased from 220pF to 470pF in your circuit. Is this to stop oscillations ? Gate drive resistors increased to 470 ohm Gate clamp zeners increased from 12v to 13v . Diodes changed to 4148's C3 on the input leg has been changed from 330pF to 470pF. C10 and C11 increased from 47nF to 68nF. Values at output zobel(?) changed I would be very appreciative if you could take the time to explain to me the reason why these values have been changed. |
![]() |
![]() |
#36 |
diyAudio Member
|
I can't explain as this was not changed by me
This was the kit from a hong kong electroinc company |
![]() |
![]() |
#37 |
diyAudio Member
Join Date: Jun 2013
Location: Perth
|
|
![]() |
![]() |
#38 |
diyAudio Member
Join Date: Apr 2005
Location: Buskerud
|
Tran, not re.
Snigger. R |
![]() |
![]() |
#39 |
diyAudio Member
Join Date: Nov 2018
Location: N/A
|
I built six of the Tilbrook amps in 1982 for a 3 way active unit. The design was published in Germany in elrad magazine in 81. It took me quite a while to cure a wild oscillation of each and every amp - R29 in the kits didn´t look like but was wire wound. Replacement solved the issue once and for all.
Regarding replacement of the BF´s, there obviously is NOS of a GDR/CSSR-equivalent for the BF 470 (Tesla KF 470) available here for peanuts: https://www.pollin.de/p/pnp-transistor-tesla-kf470-131455 |
![]() |
![]() |
#40 |
diyAudio Member
Join Date: Dec 2011
Location: near Stuttgart
|
I also built the Elrad PowerMosfet from 1981 and solved the oscillating , with 5 x 1 Ohm resistors in parallel, later when dig out again with 0.22 Ohm Metal band resistors (MPC-71) for the source resistors of each MOSFET. It's still running and remaind me at the former HITACHI HMA-7500.
|
![]() |
![]() |
Thread Tools | Search this Thread |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
BOZ problems - PLEASE HELP!! | Tieftoener | Pass Labs | 12 | 7th March 2018 08:11 PM |
ESP P3A problems | cantabile | Solid State | 31 | 31st January 2007 11:36 AM |
Sub Amp Problems Thanks! | crippledchicken | Solid State | 2 | 10th January 2007 07:17 PM |
Any problems with Fun-Tak (tm) on the PCB? | fotzepolitic | Solid State | 10 | 1st February 2004 04:35 AM |
New To Site? | Need Help? |