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Discussion in ' Solid State ' started by Ruxman , Jul 29, Log in or Sign up. Messages: I have an amp with a blown channel. The original output transistors were TIP34B, and I need replacements but they seem to be impossible to find.
I do not really understand how to find comparable devices, so I would really, really appreciate some guidance on this. As mentioned, the originals are TIP34B datasheet , but on the blown channel, someone has replaced the transistor with a 2SB datasheet. I can find these, but I do not know if they're a good replacement. Any help would be really appreciated!
Ruxman , Jul 29, Messages: 1, Location: Ontario, Canada. OverLoad , Jul 29, Messages: 4, Location: Mass. Just curious. Good Luck. Last edited: Jul 29, Messages: 2, Location: BC, Canada. Messages: 5, Location: Livonia, Michigan. Dynaco used TIP transistors in several of their designs.
Dr Tinear , Jul 29, It's an OEM amp Thanks for the advice so far. Last edited: Aug 4, The 2sb has a higher voltage rating, and the is rated at higher current. Unless the amp is running at high voltages, they all should work.
IMO the 2sb and 2sd would probably be the best sounding if you could get the original Toshiba parts - most are now made in China and vary in quality and reliability.
Some are probably very. Good luck. Basically it sounds like you have a smorgasbord of output transistors. Without more info it's hard to say what was original. Thanks a lot for the help!
This is very educational and fun for me. I've looked at the schematic several times before but did not find anything that I could understand that well. Now, with your insight, I looked again and found something of great interest!
That confirms that the TIPs are not original! I have taken out the TIP on the blown channel and everything is shorted. No matter where I put the probes, I get continuity. Maybe that is why it has been smoked? Also, a small 1uF cap had exploded on this channel. I've replaced it. Messages: 6, Location: Oregon, land of magnificent stumps. A total power supply voltage of 88V is really asking too much from anything in the family, even if the devices were pre-tested above that voltage with a curve tracer.
BinaryMike , Jul 29, Well bloody hell! You had a schematic the whole time?! OK, so the mystery is solved. They spec'd 2SB and comp 2SD as suitable as well.
Back to original question. Tip 35C and 36C are higher powered versions and are still available. Can be found at most electronic distributors.
In stock at mouser. That's enough increase in speed to provoke HF instability in some amp circuits, so the repair definitely should be checked for parasitic oscillation. If it's clean, then overall amp performance is likely to be improved.
BinaryMike , Aug 1, I ordered a new TIP transistor before starting this thread. It arrived today, and now the amp works again. I do intend to get the proper transistors soon, this was just a test.
However, the DC offset is very high. Or is this caused by another part in the circuit? There are no adjustment points for DC offset in this amp. There are seven transistors in total on each power amp section. The two outputs, and then very near those, 2SA and 2SC And then there are three more, I have not looked at them because they are hard to reach, but according to the schematic they are either: 2x 2SA or 2SA And finally, 2SC or 2SC Is it likely that any of these could be causing a high dc-offset?
If anybody is interested, here's a schematic of the amp GIF, kB. Ruxman , Aug 4, Messages: 1, Location: Dallas. Those are about as close as you can get. FootFungus , Aug 4, Thank you for the suggestions. Man, it is difficult to find these output transistors. I guess I'm going to have to go with those, but I've gotten the impression that they are not entirely suitable. But I have no way of making sure they are matched. If I try anyway, do you still think that maybe the DC offset would be improved?
Messages: 57, Location: Hertfordshire, UK. Hyperion , Aug 4, So I take it that these two transistors are the only thing that is relevant for the dc offset? A recap, for example, won't help at all?
What about getting proper output transistors? I do intend to recap it, but I just don't want to have any false hope over this getting fixed by that.
How do you get matched pairs of transistors normally? Just get a big bag and test them? No easier way? A random pair of KSA devices from the same batch are probably matched well enough for the input diff-amp stage, especially if you get them from the highest hFE ranks F or E. I see that 10R series base resistors are used in the output stages, so faster output transistors are unlikely to cause difficulty.
Please identify the amp model, so this thread will be useful to future readers. BinaryMike , Aug 4, You must log in or sign up to reply here.
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Need a modern replacement of a TIP34B transistor
FT2955 Datasheet, Equivalent, Cross Reference Search
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