Yaqin MS-300C Upgrade

[mroboto]

Hi,

I do not have to complain about this amplifier,but I think,I am sure we could improve it.

I don't want to ask about tubes rolling,there already are a lot of threads about this on the web.

I will take my time,think about that before i begin any work on this,but meanwhile,I wish I could have a better idea about what I could do.

So, I wonder,if you have this amplifier,what would you do with it,or what's the first thing would you do with it?

I know I could probably make unnecessary or bad changes, and I would like to avoid, especially with the price of some brands parts.

So anyone is invited to give their opinion or debate on this thread.


Input tubes:12AT7 (12AT7WA RCA 6201 installed)
Drivers and Cathode followers:6N8P - 6SN7 - 6H8C (6N8P installed)
Rectifier:5U4GB - 5Z3P - 274B (EH 5U4GB installed)
Power Tubes;(300B-98 installed)



Direct link: http://img155.imageshack.us/img155/2032/ms300cschematics.jpg



Direct link: http://img827.imageshack.us/img827/1593/66487338.jpg



Direct link: http://img215.imageshack.us/img215/2280/73168737.jpg



Direct link: http://img718.imageshack.us/img718/1951/62769726.jpg

If you want particular/detailled pictures,ask me.


I could have made mistakes on this Original (not upgrades) non-official capacitors list.

Electrolytics

C101 22uf 450V
C103 22uf 450V
C106 22uf 450V
C108 22uf 450V

C112 330uf 400V
C113 330uf 400V
C114 330uf 400V
C115 330uf 400V

C116 1000uf 25V

C117 100uf 16V
C122 100uf 16V

C118 100uf 160V
C119 100uf 160V

C120 6800uf 16V
C121 6800uf 16V

C201 47uf 16V

Metal Film ?

C102 0.1uf
C104 0.1uf
C107 0.1uf
C109 0.1uf

C105 0.47uf
C111 0.47uf

C202 102
C203 102

C204 1uf 16V

C205 470p

C401 104

C601 103 AC400V
C602 103 AC400V


I found this info,i'm not familiar with this kind of parts.

101 = 100 pF 0.1 nF 0.0001 uF
102 = 1000 pF 1 nF 0.001 uF
103 = 10000 pF 10 nF 0.01 uF
104 = 100000 pF 100 nF 0.1 uF
105 = 1000000 pF 1000 nF 1 uF
106 = 10000000 pF 10000 nF 10 uF

 

[bOUddha]

Personally, I wouldn't even bother dusting the damn thing without a comprehensive tube roll. Why bother changing the spark plugs when you don't know what the fuel/air intake system is?

Once I plugged my new tubes in, I completely forgot about upgrades or searching for a replacement. Still happy and content with the rig after a year.:thmbsp:

 

[mroboto]

Yes,for tube roll,i already changed the stock 12At7 with good RCA's and already see an astronomical difference.

But tubes are not the most long term investment compared with good PIO's or ?,and i think the tube roll would make a better sensitive change when the signal will be mostly well cared.

So,what'the first ones to go?

C102 0.1uf
C104 0.1uf
C107 0.1uf
C109 0.1uf

Or

C105 0.47uf
C111 0.47uf

All ?

Or what could be the most drastic change i could do?

In another words,for what parts should i invest the most?

I want richer bass and sweater mids and highs.

If you know if i could safely change some values,i would like to have inputs about that too.

 

[roadtrip]

Yeah! valve rolling is fun too :thmbsp:

 

[mroboto]

The only tubes that where realy bad quality was the 12AT7 and maybe the 6N8P , i will change them next.

But at this time,i want to upgrade the amp itself.

I know,and that's for sure,that something better exist,it could not be a mistake to change them with almost anything for 5-10$ or more (each part).

Some yaqin caps market value are like 1-2$ , really cheap,and there is a reason for the best brands to cost hundreads.

 

[vincei]

Change all the ones you mentioned above, they are all in the signal path, so may as well do all of them I say...along with a tube roll, you should then be good to go.

 

[roadtrip]

Obbligato caps are excellent bang for buck!
http://www.diyhifisupply.com/catalog/21

I used the Premium's in my crossovers and MPK's in a Sansui amp in place of some of the low value electro's. The MPK's are a dynamic sounding cap, and I found the Premiums to be warm with a nice bottom end in my use of them.
I plan on using some of these when I upgrade the MC10L I have.
The premiums are in 0.1uf and .047uf @ the budget you mention. Just an option

 

[mroboto]

Thanks,

FREDYLOSOPHE on homecinema-fr tells me about russian K40Y9 PIO's ,that seems to be a good afordable choice too,i like PIO's

What about the values?

I will add my own sound signature to the sound if a add a few .* uf's

These caps are there to filter DC ,but if i want a most tremendous bass,that's where i should go?

Like 0.15uf instead of 0.1 / 0.68uf instead of 0.47

Is there big risk to do so?

I don't have an oscilloscope and knowledge to analyse the signal.

 

[roadtrip]

Hmm...I like those PIO's depending on where they are used, overall I find them to be somewhat veiled, if using Nos Russians
I prefer some of the Teflon's.

Unless you really understand this circuit, I would be very cautious about using different cap values! In some positions a small variation in values could cause instability.

Need someone with more knowledge than I to chime in :scratch2:

 

[mroboto]

A wire was too much closer to a transistor in my unit.



Now,we can see a scar on it.



Check this and post pictures of yours if you see this.

 

[vincei]

Yes that is a little close for comfort, since it's a regulator its resting on and if it gets hot enough, could melt the insulation, however hopfully the designers knew it would not be an issue and therefore would be safe to leave it.

For cap values, I would try to leave them as is, higher values may not nessessarily make things better, but could make things worst.

 

[mroboto]

the wire not just touch the transistor,but was tightened in this position.

I think everyone must inspect for this because,that could be a future issue.


Yes,about the values,i will try to keep it as is,i just hope they not act too much as high pass,and as i dont want coupling caps,i hope to take the right decision first.


PS:the original caps brand is PILCOR

 

[mroboto]

There are a delay for high tension (to protect the tubes),but it's a bit too fast.

The delay is approx 16 seconds

If the schema and datasheet of the part CD4011BE dosen't fooled me,i can modify the delay by changing capacitance of these two 100uf caps ? ( C117 - C122 )

http://img217.imageshack.us/img217/8706/delay.jpg

 

[mroboto]

Edit:

I replaced C122 (100uf 25V) for a 470uf 25V , now,the delay is comfortable at 80 seconds (compared to 16 seconds before).

That will help the tubes to live longer.

 

[mroboto]

A few years back, i decoupled each Nippon Chemicon 330uf 450V capacitors with 2uf 630V russian paper in oil and replaced few electrolytics for F&T and used 25 ot 35V Elna that i found for the 6800uf 16V, i used K40Y-9 for coupling.

A 5U4GB Philips (US Sylvania made i think) get worn very fast as i have used it only few month, i rotate amplifiers, and now the needle drops to the lowish good position on my Sencore Mighty Mite VII TC 162 tube tester, the needle was steady high before, bought as NOS.

Installed my Weber Copper Cap WU4GB so no worry about the rectifier and it sounds as good, The power transformer runs even cooler. good recommendation if you own this amp.

Added a CL-80 thermistor to AC input, you can use NTC 47D-15, cheaper. slowed the warm up time of filaments to approx. 5 seconds to be fully warmed up.

Got a Heathkit TC-2 to tests the 300B emission to have an idea, but this tester tests every 300B low, i got between 46 and 53 results for new tubes, but as i say, i have an idea if the tube is good.

Purchased a pair of PSVANE 300B-N with mesh plates, balloon shape, very good sounding tube, I keep the bias at approx 65mV to be safe because i don't want to re-ajust often, i just mesured them with my infrared thermometer and one tube mesure 240 while the other mesure 260 F° , that means probably have to adjusted soon. manufacturer recommends 80mV for 9.5 wpc, but mesh plates are more sensitive to power draw i think.

 

[chris64]

A few years back, i decoupled each Nippon Chemicon 330uf 450V capacitors with 2uf 630V russian paper in oil and replaced few electrolytics for F&T and used 25 ot 35V Elna that i found for the 6800uf 16V, i used K40Y-9 for coupling.

A 5U4GB Philips (US Sylvania made i think) get worn very fast as i have used it only few month, i rotate amplifiers, and now the needle drops to the lowish good position on my Sencore Mighty Mite VII TC 162 tube tester, the needle was steady high before, bought as NOS.

Installed my Weber Copper Cap WU4GB so no worry about the rectifier and it sounds as good, The power transformer runs even cooler. good recommendation if you own this amp.

Added a CL-80 thermistor to AC input, you can use NTC 47D-15, cheaper. slowed the warm up time of filaments to approx. 5 seconds to be fully warmed up.

Got a Heathkit TC-2 to tests the 300B emission to have an idea, but this tester tests every 300B low, i got between 46 and 53 results for new tubes, but as i say, i have an idea if the tube is good.

Purchased a pair of PSVANE 300B-N with mesh plates, balloon shape, very good sounding tube, I keep the bias at approx 65mV to be safe because i don't want to re-ajust often, i just mesured them with my infrared thermometer and one tube mesure 240 while the other mesure 260 F° , that means probably have to adjusted soon. manufacturer recommends 80mV for 9.5 wpc, but mesh plates are more sensitive to power draw i think.

Hi there ive just joined
I have the ms 300b its stock about 6 yrs old , its using jj 300b ps vane 6sn7,274b,12at7 - I cannot find anyone to re cap and upgrade this beautiful amp for me !!
it has a very slight hum and always has , it also makes the drivers pulse in & out when I first switch on -- I just wish I could find someone to check it over -- or give me detailed info on re capping myself

 

[mroboto]

Hello and welcome,

Have you replaced the rectifier ? I realyzed my MS-300C is a rectifier eater,

I need to replace the two 330uf first caps that are in series for 80uf caps, ordered two 100uf finally, because 5U4GB max rates 1st cap is 40uf or two 80uf in series.

The model MS-300B is different.

There is a thread in french where maybe you can find some information here: http://www.homecinema-fr.com/forum/...es-haute-fidelite/yaqin-ms-300-t29851288.html

Take digital pictures and use Windows Paint to note everything you may need to remember like polarity and values once old caps have been removed and you got the new ones.

Also need
30 or 40W soldering iron
Solder Sucker
solder

 

[chris64]

hi thanx for relying
all the tubes are new and the 274b ( psvane ) is just out its box
to be honest the amp sounds wonderful - just feel it needs a service and put some decent caps in there -- I also run the xiangsheng pre amp and all this ends up in fostex back loaded horns
I'm fairly confident to go in there but could do with diagrams etc to save time and headaches

 

[mroboto]

I found what you search for the MS-300B model.

Click at the right of Document Joint
http://www.cjoint.com/c/FLzaviITOvB

 

[mroboto]

Done what i think is final mods on my MS- 300C, and it work and sound very great

Replaced C112 & C113 330uf for 100uf 450V Kendeil (top left) (just after the rectifier)



Added 4.7uf 630V CBB and 0.1uf 1000V Ceramic disc as decoupling of the top right caps right (after the choke)



Added a socket saver under the rectifier so he stay cooler