Yamaha Amps

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MxR
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Re: Yamaha Amps

Unread postby MxR » Tue Aug 04, 2015 10:30 am

Greetings,

Recently I have received a TA 90 system in service. The PE 100 preamp seems to be fine, while the TS 90' chassis needs some attention (missing transistors, etc.). Could anyone provide me with the TS 90 circuit diagram, or even better with the service manual? Or at least a hint, where to look for such things. I could however do a reverse engineering and make a shematics diagram from analysing the chassis circuit in current state, but the problem is that some parts in the circuit are missing.

I was also looking for some sort of contact on Yamaha official web page (if they could provide me with schematics or service manual), but found nothing useful about vintage amps.

P.s. Sorry for my not-so-good English (I come from Slovenia)

Best Regards
Martin

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Buzzard
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Re: Yamaha Amps

Unread postby Buzzard » Tue Aug 04, 2015 3:11 pm

Hi Martin, Welcome to the Yamaha Forums. :D

I think you should try to contact Yamaha for the service manual needed.

Image

Some years ago, I got a service manual for my own TA-120 for free from Yamaha Scandinavia,
that was a GREAT HELP, getting my TA-120 back to perfect working order.

The TA-30 , TA-60 and TA-120 manuals are also awailable here: http://bmamps.com/Tech_sch.html , but no TA-70/TA-90 manual

You may be able to find a manual online at a cost, therefore try Yamaha first.

Best Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea: Humlebaek , Denmark.

MxR
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Re: Yamaha Amps

Unread postby MxR » Sat Aug 08, 2015 10:11 am

Thank you for your response. I have written to Yamaha about TA 90, but no response for now. But even the schematics for other TA models are a little help. The circuits are quite similar as far as I have seen.

Anyone, that has a TA 90, could I ask, which two types of transistors are for the AB class (push-pull) power stage? Are 2N3055 (npn) and MJ2955 (pnp) the correct ones?

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Re: Yamaha Amps

Unread postby Buzzard » Sat Aug 08, 2015 10:46 am

MxR wrote:Thank you for your response. I have written to Yamaha about TA 90, but no response for now. But even the schematics for other TA models are a little help. The circuits are quite similar as far as I have seen.


When I asked Yamaha Scandinavia for support and a service manual for my TA-120, I gave them a full report of the defects, including pictures,
and linking to this post to show them that I'm a serious Yamaholic :wink:

The support is amazing, they were as exited and determined as myself to get the vintage amp up and running.

The only catch is that workshop/service manuals are for workshops and dealers only, but when it comes to vintage gear, they usually go the extra mile to help.

With a bit og luck, your Yamaha support will get back to you with the schematics you need, if not, I'll see what I can do. :D

The amp in the TS-90/TA-90 is the single most powerful TA transistor amp pulling(and pushing :lol: ) 3 speakers.
It is similar to the other TA amps, but has a somewhat more robust output stage.

Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea: Humlebaek , Denmark.

MxR
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Re: Yamaha Amps

Unread postby MxR » Mon Aug 24, 2015 7:01 pm

Quite some time passed since my last post (hollidays, waiting for components, ...). Still no response from Yamaha Austria yet, not even an e-mail to say, they can't help me. Can you please give me Yamaha Scandinavia's e-mail? Hope there will be more luck.

When I got the amp in service it seemed quite a mess. There were 2 transistors (2N3055) istead of 4. 2 transistor sockets were empty. Later I ordered a complementary PNP (MJ2955). After measuring DC voltages (+75V on 2N3055 collector's pin) and trying to figure out, which trans. goes where, I plugged the thing on 230V AC (with a light bulb in series), and the bulb went ON. It seems that someone was messing up with the amp, and made things even worse. It'll be quite a challenge to make the amp play :).

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Re: Yamaha Amps

Unread postby Buzzard » Mon Aug 24, 2015 8:19 pm

Since I have only one P-100 (preamp) shared with two power cabinets (TS-60 and TS-90), I could actually use a servicemanual myself.

I'm working on it, and hopefully I get response soon. :D :wink: :D :wink:
.... but do tell if you have any luck. :roll:

Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea: Humlebaek , Denmark.

MxR
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Re: Yamaha Amps

Unread postby MxR » Mon Aug 24, 2015 9:07 pm

As far I have seen so far (also from the TS 30/60/120 schematics), these amps use a little different push-push (class AB) aproach. Instead of clasical complementary output transistors (NPN and PNP) with in-phase signal for both of the transistors, here the output transistors are the same type (NPN) and in 2 lines, fed by 2 signals, one in-phase, the other out-of-phase. That's why, there is a small transformer located on the PCB. Interesting aproach. It reminds me on tube-amp push-pull circuits.

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Re: Yamaha Amps

Unread postby Buzzard » Mon Aug 24, 2015 9:21 pm

When I fix amps, I only do the fairly simple, elementary repairs. :!:

IF, it gets really complicated, I usually get expert help from someone else.
I just e-mailed Yamaha expecting to have response in a few days.

Is everything else working on your TA-90 :?: preamp :?: speakers :?:

Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea: Humlebaek , Denmark.

MxR
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Re: Yamaha Amps

Unread postby MxR » Mon Aug 24, 2015 9:42 pm

When it comes to such repairs, I don't want to give up. I am a student of electrical engineering, so such things to repair are also good practical work.

I have also written to Yamaha UK about the amp. Hope to get better luck this time.

The speakers seem to be fine (at least visually, and with DC resistance measurement (around 2 ohms = 3x 8 ohms in parallel)), the preamp needs only a bit of cleaning on the inside, otherwise, it works. I plugged in a guitar, and on the otherside my PA system.

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Re: Yamaha Amps

Unread postby Buzzard » Mon Aug 24, 2015 9:53 pm

Better check the speakers, one at a time, actually playing music through them,
just to make sure that the coils are not warped. (scraping against the magnet.)

Image

If any of them are damaged, they are hard to repair, and almost impossible to replace.


Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea: Humlebaek , Denmark.

MxR
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Re: Yamaha Amps

Unread postby MxR » Mon Aug 24, 2015 9:58 pm

Will check again, maybe also with some other amp (individual speaker test).

Thank you for your help so far. Will report if I make some progress.

BTW, are these Yamaha speakers also good for bass guitar?

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Re: Yamaha Amps

Unread postby Buzzard » Mon Aug 24, 2015 10:12 pm

MxR wrote:BTW, are these Yamaha speakers also good for bass guitar?


The Yamaha JA4001 speakers are only 30 watts each, if you use a bass, BE VERY CAREFUL :idea:

They are made for organ/keyboard/pa and acoustic guitar, and fine for electric guitar with pedals.

my fully restored TA-120
Image

Regards
Peter
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea: Humlebaek , Denmark.

Daviedawg
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Re: Yamaha Amps

Unread postby Daviedawg » Thu Aug 27, 2015 10:03 am

Peter
I like that a lot of the Yam amps you own have a tilt stand. Every amp should have that to send the music into the air not onto the floor. I believe that the sound pattern from 4x12 type cabs is pretty much a narrowish vertical band. Yet that layout is what you see on stages everywhere. Vertically angled front (as early versions of Watkins Dominator) on a tilt stand should be much better for sound spread.

But then nowadays even ZZ Top mike one amp through a PA but still have a huge wall of 4x12s.

Dd
Yamahas:
SF500 Sunburst three colour Aug 1978
FZ1000 Black Sharkfin offset vee July 1986
SC400 red transparent 1982
Fazer 600cc gold and black 2000 25,000 miles and rising. Sorry 30,000 miles.

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Re: Yamaha Amps

Unread postby Buzzard » Mon Aug 31, 2015 7:58 pm

The Marshall walls .................

Image Image Image

They are not always fake, but seldom playing at full blast.
The performers prefer to have monitors to be able to hear the rest of the band.
The real powerblast usually comes from the PA system located a bit away from the band. :idea:
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea: Humlebaek , Denmark.

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Re: Yamaha Amps

Unread postby Buzzard » Mon Aug 31, 2015 8:25 pm

Daviedawg wrote:Peter
I like that a lot of the Yam amps you own have a tilt stand. Every amp should have that to send the music into the air not onto the floor. I believe that the sound pattern from 4x12 type cabs is pretty much a narrowish vertical band. Yet that layout is what you see on stages everywhere. Vertically angled front (as early versions of Watkins Dominator) on a tilt stand should be much better for sound spread.

But then nowadays even ZZ Top mike one amp through a PA but still have a huge wall of 4x12s.

Dd


Yeah, the Watkins Dominator is a beauty, especially the blue ones, the tan colour looks nice too:

Image

Image

This brand was intil now unknown to me ...... NICE :!: :idea: ((i))
Yamaholic, Guitars, Amps and Bikes. :idea: My Guitars: viewtopic.php?f=24&t=7004 :idea: Humlebaek , Denmark.


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