• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

yaoin

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boboo

boboo

Member
Joined 2008
I think finaly have wined up in the right place.

I need help from you guy whom knows more about those heatproducing amps than I do.

I have this 23000 year old harman kardon 730 twin powered receiver which works excellent but the selector switch is gone and all the lights has died some 100 years ago!
Well his got tyred and I can't get any selector switch as replacement to it nor those little bolls to lit up this oldie.

Maybe somebody out there can help me out to get me some of those spares parts to it..

Anyway, I brought this Yaoin Chinese amp MC100B with a lot's of eggboiling heat producing things in it and I believe you guys call those tubes, valves or pipes whatever, hot are they like h.....l!. I think they are those KT 88 frying pans

So, there is no base! It is, but nothing if I can compare whit the harman kardon.
So I was wondering why? Does it help if I got an external preamp with loudness controll or an eqaulizer? Tell me what's going on because I don't hear that big bang as I'm used to get from the harman.

So it's a big disspointment so far and nothing else. It's got to move this (look at the pic) x2 with a big bang which my harman does.
 

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cuibono

cuibono

Member
Joined 2006
As to the lack of bass, that is not too uncommon, but there are several possible causes. We'd need to look at the schematic, and know more about your system - like the speaker type, impedance and cables. It's likely to be lousy amp design.

Maybe someone on the board has modified the amp you have and can help. Have you tried searching?
 
boboo

boboo

Member
Joined 2008
cuibono said:
If you give some details on the parts you need, maybe someone could help find replacements. How many poles/throws for the selector switch? Posting a picture would help..
Click to expand...

I don’t know what it is but something is very mysterious with this Harman. ?????
I have tried to replace it during many years now and listen to lots junks, both with high end amps and receivers like Technics, Sony’s Akai’s Revox’s , Sharp’s Sansui’s and you name it they were all in my living room on try but no one comes near by.

Is somebody out here who can tell me why?

I’m an artist and photographer and very sensitive when it comes to sound. Now I brought this heater to amp (yaoin) weights six times as much as a Harman and there is no bass it’s like a sopranos comparing to the Harman. Anyway I have heard now that all frying pan owners have bad bass they just don’t want to say it or never heard a Harman. Its moves like hell my glasses shaking and dancing in the kitchen and just looked what I got it’s all JBL except some Piezzo on the high top. It’s low and high bass low and high mid, drivers in wooden horn.

Okay back to the subject

There is some things written on the switch but it’s deep inside in the case.
It says PCB147F 94VI than bottom I think it’s just marking the position and finally some additional figures like 4551-7156

The selector had am, fm, aux1, aux2, phono1, phono2,

But if any of you can supply me with volume, ballance and treble would be nice too.
 

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boboo

boboo

Member
Joined 2008
cuibono said:
As to the lack of bass, that is not too uncommon, but there are several possible causes. We'd need to look at the schematic, and know more about your system - like the speaker type, impedance and cables. It's likely to be lousy amp design.

Maybe someone on the board has modified the amp you have and can help. Have you tried searching?
Click to expand...

Okay the speakers it’s mostly all JBL .

In one channel for example I got 2x15” bass split in to two, very low so called air suspension cabinet and high bass closed cabinet.
Than, you got two drivers in a wooden horn low and high come in different size with 2 x 4” which overlap the two drivers and just for colouring the sound.
On the top there is one JBL 075 and four Piezzo discount.

Now the other side is almost the same but there is one 15” sitting in one big cube very low frequented faced to the flour to balance and colour the other sides air suspension cabinets sound. I got a very rich sound! That’s why it’s so difficult to find other amps because I’m loosing it.

Yeah I tried to get answers everywhere on the MC100B and heard that many tube stuff even more expensive well known brand has problem with the bass they are intend to be floppy.
This is happened with me when try to replace the Harman before with other brands but they were not tube.

And finally, the cables? Well the 1 1/2” inch speaker cables are okay isn’t it? So as the pro cables between the CD , tuner and the reel to reel.
 
boboo

boboo

Member
Joined 2008
Lowrider said:
You can get very good bass with frying pans, particularly with sensitive speakers like you have...

You may have to change a few parts in your amplifier, as I did in mine, try to get the schema and ask the experts, thats what I did... :rolleyes:
Click to expand...

The schema is no problem there is a guy here who have it but I can't e-mail him because I'm new here or what so ever and the system not alloud me to do that.

Finding an expert here in Sweden? Space age, nobody knows this things any longer here! Digital and throw away or change the card that's what they know here.

If I were living in Russia or Hungary it would an expert in every doorway. that's bad it is here:
 
Alastair E

Alastair E

Member
Joined 2004
doctordiesel.co.uk
Have you tried a little switch-cleaner in the Harmon amp...? This could help the controls, But dont use too much (I prefer the older equipment best too!).....

I believe Tubetvr, who is a member here lives in Sweden, Maybe he can help you....

I have no personal experience of your new amp, but have heard those are low on bass, but dont know why sorry...
 
boboo

boboo

Member
Joined 2008
Alastair E said:
Have you tried a little switch-cleaner in the Harmon amp...? This could help the controls, But dont use too much (I prefer the older equipment best too!).....

I believe Tubetvr, who is a member here lives in Sweden, Maybe he can help you....

I have no personal experience of your new amp, but have heard those are low on bass, but dont know why sorry...
Click to expand...

Well hopefuly he going to see my thread here and answer.

Yes it had been cleaned many times but it's just don't work any longer. I guess I have passed the cleaning limit just one time for many. :) But if I got the parts I need I will fix it!

Yes they are a little bit to thin with out power and it doesn't matter if the volume is low or high it seems that the amp not giving much power to the bass. Even if power overated by the manufcture should be working as the tranformators are big twice the size of the harman and it's a class A with 30/60 watt. It's weights 30 kilos!

What is the secret of the Harman?
 
boboo

boboo

Member
Joined 2008
Lowrider said:
I am Portuguese living in Latvia, dont speak the language, nothing...

I buy everything on the internet, all my help is virtual, still I did several mods on my amplifier... :angel:

http://www.melorib.com/diy.html
Click to expand...

Well. hello Portugal.

If I got picture like that one on the site you have pulished and somebody tell me what and where I would do it myself to, but this amp is proboly new modell and not many people own one yet. Therefore not many publications either
But if somebody coming across something please do not hasitate to tell me.
 
boboo

boboo

Member
Joined 2008
Lowrider said:
I started a few months ago with a picture of the inside I found on the web, and it was not exactely the same as mine... :xeye:

After the first mods, removing all the stuff I didnt need, I found the schema, I am sure you can get more support than this in Sweden, tube amplifiers are reasonably simple any way...
Click to expand...

Yes you right but it wouldn't be easy to find somebody but I will try. It's might not be possible to fix it at all so untill that I put this one up for sale yesterday.

Probobly going to get one 730 twin again on the net.
 
boboo

boboo

Member
Joined 2008
Lowrider said:
It will be very difficult for me to return to transistors, after trying tubes... :whazzat:
Click to expand...

Yeah that were my idea too. To try something different but it's got to work as far as I consider it's more like a project as most of those guys who have tube is modify and rebuild. I't a project not a ready use equipment. I didn't know that. :)

I got to work too and earn a living. :) And I have a different accupation too. :)

So untill I didn't get or find help I can't use this. No sound. It's okay on mid and high but nothing else and I'm not sure that it's better than the harman.

I don't understand because Yaoin are well known of other amp they manufactured. This one is bigger and post to be better as it's mainly seem to be twin in one chassy. It could be so to that is impossible to modify so I'm going get to be satisfied. I got a lot's of speakers which must be moved around! :)
 
O

OXAUDIO

Member
Joined 2006
Yaoin

Boboo,
I sent you an email reply BEFORE I had read your posts.
Having other things to do now, also to earn a living, I will get back to you when I have had time to think more about it. In the meantime, the schematic for the Music Angel Amplifier can be found(and downloaded) in a post by 'jesabel' about MA Amps. on this forum
Regards from
OXAUDIO
 
boboo

boboo

Member
Joined 2008
Lowrider said:
Before I had a Cayin A-88T, and it sounded very good, after the seller replaced a couple of tubes...

Same with my current Classic 16.0, of course it can sound even better, but I would never get into the DIY mods if I didnt like the sound of tubes already...
Click to expand...

what do you mean by replacing the tubes. Was the tubes dameged or?
Mine is completely new get it home last week. So I believe the tubes are okay. I mean 20 hours must any tube manage don't they? :)
 
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