Semiconductor Sources

louye2

Member
Would someone please recommend some reputable semiconductor sources for vintage audio?

I blew the output transistors on my Kenwood KR-720 (too painful to discuss) and need to replace the following parts:

2SC2577
2SA1110
2SC2590
2SA1102
0.22 OhmK resistor (MPC78)
0.22 Ohm, 3W resistor

There seems to be some discussion in AudioKarma about the importance of OEM parts and the danger of buying counterfeit parts from eBay. I've looked in Mouser, Electronica, B & D, OnSemi, etc. I get mixed responses from out of stock to suggested replacement part numbers.

Now, I'm confused and don't know where to turn to get good parts from a reputable vendor. Your advice and recommendations are greatly appreciated.

Thank you.

Louye2
 
Best thing to do would be to examine the datasheet for the originals and try to spec replacements with suitable specs.
 
I found the following information for substitutes:

2SC2577: 2SD895 2SD586 2SC2527 2SC2484

2SA1110: nothing listed

2SC2590: nothing listed

2SA1102: 2SB775 2SB616 2SA1077 2SA1060

I hope this helps some
 
Have had good luck with bdent.com - lots of the older japanes (2sa 2sb 2sc 2sd) transistors. Even if they don't have them, if they have a listing, they usually have a spec sheet (click on technical specs then view specifications if the link is there.) Mouser is usually a little cheaper, and Digikey has the largest overall selection. Bdents only problem is they don't have any decent search help. Good luck.
 
For the 2SC2577 and A1102 I'd suggest using either Sanken 2SC3855/2SA1491 or 2SC3856/2SA1492 (www.bdent.com is a source) or I'd suggest taking a look at the ST Micro 2STC4677/2STA1694 or 2STC4678/2STA1695 from Mouser/Digikey/Future/Arrownac.

For the 2SC2590 and 2SA1110 you might look at the KSA1220A/KSC2690A which are widely available. 2SA1358/2SC3421 and 2SA1248/2SC3116 are mentioned as subs (check www.bdent.com). All these are slower in FT but otherwise exceed the originals. Another option might be the Toshiba 2SC5171/2SA1930. As fast as the originals, and much beefier. The pinout on the 2SC5181/A1930 is reversed from the originals plus the packaging is different, so if the originals are mounted on the heatsinks they may not work well.

If these are blown, I'd check the VAS stage transistors feeding the drivers.
 
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Thank you to everyone who responded. I will check out the various substitutions A local electronics supplier has all the transistors available from NTE. For example, 2SA1102 is replaced by NTE37. He claims the NTE parts meet or exceed the OEM specs.

Is it a bad idea to install NTE transistors? Am I likely to be disappointed with their performance?
 
I've been reading/learning alot on this forum as these guys are very knowledgeable and helpful.

The links/suppliers they have given you have worked well for me.

Most of them say stay away from NTE parts as their origins are undocumented/counterfeit.

Hope this helps,Bob
 
MCM Electronics

MCM had all the old Japanese transistors. Good prices, but high shipping costs ($8.99) for a tiny package. My old Kenwood is happily playing music again.

Thank you to everyone who responded to this thread.
 
I just had a very good experience ordering from Audio Lab of GA. Shipped immediately, arrived quickly via USPS, and shipping was cheaper than FedEx or UPS. They carry quite a few Japanese transistors.

http://www.audiolabga.com/
 
I just had a very good experience ordering from Audio Lab of GA. Shipped immediately, arrived quickly via USPS, and shipping was cheaper than FedEx or UPS. They carry quite a few Japanese transistors.

http://www.audiolabga.com/

Great reference! Thanks a bunch!

I'm working on a spreadsheet with the transistors as columns and specifications as rows. I'll share once I get updated as I am going through datasheets at the moment and trying to shave some time with experienced service references.


For cross reference on this thread also... I added info regarding my situation and questions on this thread:
http://audiokarma.org/forums/index.php?threads/kenwood-kr-720-blown-left-speaker.674482/
 
I blew the output transistors on my Kenwood KR-720 (too painful to discuss) and need to replace the following parts:

2SC2577
2SA1110
2SC2590
2SA1102
0.22 OhmK resistor (MPC78)
0.22 Ohm, 3W resistor

Welcome to the ever-exciting world of vintage gear repair! ;)

I am no expert and I'll share the following few things I've learned as long as you keep in mine these are just one perspective:

There are thousands of discrete transistors that have been manufactured and used in audio gear over the last decades. LOTS of them. The biggest difference between them is how does each perform in a given application.

For instance, one transistor model, e.g. 2SC458, might be able to do duty as a switch, as a voltage regulator, as a voltage amplifier, and more... but it won't necessarily be a _good choice_ in each of those different uses it could fill.

So, when someone (like NTE) says "KSC1845 crosses to (can replace) 2SC458", that answer is not always useful. That "cross reference" might only cover when the original device was used in a circuit for amplification but not for switching. You need the specs for a given transistor _as used in the circuit_ along with the specs of a new replacement device to really get a good replacement match.

If you only look up a susnstitute in a cross ref guide, or only use an online substitution site like alltransistors.com", or only use a thread here on AK that gives out non-application-specific cross reference, then you could easily put the wrong substitute in place while feeling like you're doing things right.

So, when I started out, I found asking here on AK "what is a good substitute for 2SC1344" when I added "for use in the preamp board of my Pioneer SX-450 at component number Q402" was the most-successful and least-expensive way of finding good substitutes. And I learned a lot about transistors from reading all the posts from many members during that thread.

A great example was finding a substitute for a preamp low-level amplifier like 2SC458. On my own I had guessed KSC945 would be perfect, only to have many people teach me "yes, the KSC945 will work, but it isn't as low noise as the KSC1845. So, for audio preamp work, use a lower noise device so long as the other specs work, too, and your resulting circuit will operate the same but it will be quieter than before."

In this particular case, it sounds like you have reasonably starts with searching for an original transistor on Mouser.com or similar, only to find out Mouser's database of cross references doesn't show an exact-replacement modern-production device. Perfectly understandable.

Most 60's to 80's transistors aren't made any more, so there are few modern direct replacements. That's ok, since the modern replacement you _do_ find will be better in most if not all ways.

So, one way to get good advice on which transistor replacements to look for is to make a thread that says something like "looking for transistor substitutions" (like you did) and to include the brand and model number of the unit you're working on or the origins transistor model numbers you need to replace. That will help the interested AK'ers with some experience with that unit to notice your thread quicker and drop in to give their experienced advice. (And not just have people like me with limited experience or E.E. chiming in).

If you have the same luck Ive had here, you'll get responses that not only tell you which modern devices are good substitutes, but also _why_ they are good substitutes or _where_ they found their info. Then you better know how to fish the next time.

Good luck!
Doug
 
Welcome to the ever-exciting world of vintage gear repair! ;)

A great example was finding a substitute for a preamp low-level amplifier like 2SC458. On my own I had guessed KSC945 would be perfect, only to have many people teach me "yes, the KSC945 will work, but it isn't as low noise as the KSC1845. So, for audio preamp work, use a lower noise device so long as the other specs work, too, and your resulting circuit will operate the same but it will be quieter than before."

Good luck!

Thanks Doug. Yeah... I hear/read ya.

Overwhelming the number of options. I've been looking at making a ELF-ULF-VLF active mini-whip antenna for E-fields for use with a SB1095 that I am going to modify to lower the noise and need some components for that, two Klipsch ProMedia 2.1 need repair/upgrade and the Kenwood KR-720 needs repair (volume is low on the AM/FM speakers and headphones though seems OK on the phono input, plus only a green light on the power meter) so am working on reviewing some chips and transistors also for the audio range and mainly wondering about lowering the noise floor in general on any system.

From reading other posts and reviewing, so not having to change the circuit other RLC/LC or filtering or phase properties..., I want to stick with specifications that are close to specification as I can get. Great call on the noise being a spec that can change and be lowered! I've found some transistors made by ST aren't stocked as much as used to be and those perform a little better compared to the TI transistors. There are audiophile higher dollar components also I am not familiar with. However, the Burr-Brown chips are impressive as well as some of the Analog Devices chips... but those are IC amplifiers and a different circuit design... even if cost more.

Though for the vintage gear... integrating IC amplifier circuits would require a thorough overhaul to incorporate modern designs so I am sticking with repairing first... then maybe using some of the components for testing (depending on the sections of the circuit capabilities) for other gear applications. I need to read more and apply more hands on too.

This article got me thinking more about typical receivers as radio receivers and I figure I can modify to increase range if I need. http://www.americanradiohistory.com/Archive-Elementary-Electronics/1970/Elementary-Electronics-1972-05-06.pdf (see pg 45 of the PDF or 49 of the magazine) So, eventually, I will be needing to test the frequency ranges and tune though the KR-720 looks spot on in FM mode. AM I am not receiving anything and I suspect the antenna... though I may be wrong. For now, output and bias testing once I figure out the ideal candidates for replacing whatever is wrong. I tend to research and overthink before I tear into... of which I really need to perform a visual inspection on this unit.


I guess to clarify the Kenwood KR-720:
My situation is a really low volume output in the headphones and both channels... I think from the Tuner section only since the Phono section seems to output OK in each channel.

Looks like I need to measure and adjust the bias and output per the manual. I'll take the cover off... inspect and photograph if I notice anything that stands out. I'll report back once I do that.

Any ideas what might be causing the AM to have no output and the FM to be really low in volume at the headphone and speaker outputs?

I am also noticing the Power Meter isn't working either other than at zero where is a green light. Any ideas regarding? I see this thread noted repairing with an LED as a modification.

Thanks and Good Logic I hope (& have faith)! :)
 
Have you checked all the power supply outputs?

Several times Ive found that a board in a unit, e.g. the FM board, wasn't working due to a failing cap, diode or transistor in the power supply. A really common example is a transistor on the power supply board used to regulate power going to the the FM board getting to hit and failing. The rest of the unit works fine, but one board doesn't due to a failure in its part of the power supply.

So, an early check for me is "are all the outputs in the power supply outputting the correct voltage?"
 
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Have you checked all the power supply outputs?

No, I didn't check. Thanks for the reminder. For some reason I shy away from power supplies... though I did just check since this one doesn't look as dangerous, I'm more confident in my skill with testing (taking precautions) and found some strange readings.

For the outputs from the transformer I get 0V, 30.3V, 0V, 30.4V and 18.2V AC reading the output from the back of the chassis forward. None of the transformer outputs were open and they all tested conductive. The schematics coming out of the transformer seem to only note numbers I don't see anywhere and two jumpers (I guess thats the term for J) (0V-21,17.3V-26, J46-23, 24 and J47-25). See attached "KR-720... ...Stage.jpg"

D55-D56 anode side was -40.6VDC Seem high, though logical.
D53-D54 cathode side was 40.3VDC Same as I noted above.
D57 was reading 18.1VAC and on the anode side -24.4VDC. That seems logical.
D58 was reading 00.6VAC and on the anode side 0VDC. Lucky charms ain't fixin that. :D

D58 has a strange shorted moment when diode testing also where the conductivity beeps... then doesn't. Guessing D58 is bad and from the specifications... I don't see why the differences in the voltage readings since looks like the D57 cathode goes into the D58 anode. Logically confused. What do you think the best diode to replace D58 is, W06B... 1N4005? If the W06B diode is 150PIV, 0.75 Amp, then looks like a 1N4003 will do.

Guessing there is more that is bad too, i.e. other components or traces.

I also noticed some conductive adhesive that I am guessing is that way due to electrolyte leaked maybe from C161 or C162... not sure which is which yet. I've read the adhesive can become conductive over time also... and this is my first time experiencing. I was measuring ~4VDC also in that adhesive surface by the corrosion in the image (can see poke marks) and on the opposite side had ~-11VDC readings on the adhesive surface. Definitely different and new to me experience.

I need to take the chassis bottom off next and inspect underneath and probably should desolder the C161 & C162 to test out of circuit with the LCR-T4 meter.

All the readings were with the positive probe and the com aligator clipped to the chassis other than the conductivity/diode tests.


Awesome reference regarding "Noisy Transistors You Should Replace list" and "Low Noise Transistor list". I'll add that info to my IC-Transistor spreadsheet. Thanks again!
 

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Maybe you popped the F1 fuse when you measured D58? As you said, "looks like the D57 cathode goes into the D58 anode" Once the fuse blows, the transform is "floating" (no ground connection) and will measure strange. My 2 cents.
 
No, I didn't check. Thanks for the reminder.

For the outputs from the transformer I get 0V, 30.3V, 0V, 30.4V and 18.2V AC.

What do you think the best diode to replace D58 is, W06B... 1N4005? If the W06B diode is 150PIV, 0.75 Amp, then looks like a 1N4003 will do.

For me, I always start with the power supply and reassure myself that it is providing the various B1, B2, B3, etc. output power that all the other boards need. If not, the other boards will ever measure out correctly.

I most times rebuild most/all of the power supply, but that's more from OCD than anything practical.

Sounds like your transformer is operating. So, your main amp should be expecting a dual rail supply at +30 and -30 (or a single rail around +60) from the 30v 0v 30v wires on the power transformers secondary. And the single 18v secondary will end up supplying 13-15 v to all the othe r boards (or sometimes lower).

I didn't follow your powe supply output reasons. Does each of the 2 to 4 outputs measure as the schematic indicates? Anything 10% or more lower than schematic figure for that output?

I have never thought to measure the conductivity of a large cap's glue as I always, always replace them. Its a good idea, though, and any of those globs of glue that measure any kind of voltage would push me to pull and replace them.
 
Maybe you popped the F1 fuse when you measured D58?

Fuse test good thanks.

Waiting to read some feedback regarding what would cause that D58 failure so maybe I can consider desoldering and testing more than just the two 6800uF 42V caps. I don't know where else the corrosion on the jumper and conductivity on the adhesive would come from. Guessing the caps leaked and maybe did something strange. I don't see a connection on that power trace/rail to the diode. Not sure, maybe just went bad.

I was also wondering about what can be done to get filter the small voltage spike that is a noise and maybe a .25mV DC spike in the speaker outs too when I turn on. Would that be from the caps bad also or something totally unrelated?

Maybe I can start a new conversation also. Looks like threads are called conversation on this forum.
 
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