Hello,
I am currently the proud owner of three MM 130HD212.:
N/S C006227
N/S C007686
N/S C007943
Fan of the group Dire Straits for more than 25 years, it is quite naturally thanks to the MM 130HD212 that I found the sound of the first albums of my favorite group. Trained as an engineer, I quickly sought to service and maintain my vintage guitars and amplifiers. I spend a lot of time studying the 2475-130EX and its secrets! I come to share my passion with you and my work around the 130HD212!
Images:
Welcome aboard the MM site.
Welcome aboard the MM site. We have a dedicated group here, since they haven't MADE these in 30 years! Have not worked on any exports models but have seen the inside of the US versions a lot. That 130 in the pic looks nice! Cleaner than my 65 but mine has been used a lot. those corners look buffed or satiny. Is that just an illusion or did you do something to them?
Hello,
Hello,
I actually restored the fittings: chromatography for define the exact color of the original Nickel plated, electrolysis, sanding, polishing etc. : in short, a surface treatment including an additional layer compared to the original treatment: a layer of transparent varnish to prevent corrosion of the parts. It took me several weeks for obtain this result.
Quite cool!
Quite cool!
speaker update
My amps are equipped with 2 Eminence speakers with square or round al-ni-co magnets. Indeed, at
At the time, the Leo Fender factory was actually mounting
Eminence loudspeakers featuring square magnets of different
sizes and shapes. Then, around 1980, the 130HD212 model was equipped with
Eminence speakers with round ceramic magnets. Moreover,
the amp was optionally available with Electro Voice speakers
EVM 12L : I will preserve the original configuration and create now a spare of the front cabinet for two EVM 12L...
2475-130 212HD 130 MM
Good Day, Just got one of these amps, replaced all of the electrolytics that were the originals. Used good quality F&T's. The amp was played through about 5 days prior with relatively good tones - just a bit of noise probably from the old capacitors. After replacing the caps, I slowly powered the amp through the variac. once the tubes were warmed up, I checked the plate voltage, and it was 603 volts. I attempted to adjust the bias to .5VDC and the highest it would go at that 10 ohm resistor on pin 8 was about .1VDC. I double checked all of the F&T's in the doghouse, the 5 150uf 50 volt ones are spragues - they appear to be okay and soldered well. All of the capacitors were installed correctly as far as to the positive and minus sides. Any ideas? Thanks!!!
Check Bias Supply
It sounds like the bias voltage is too negative. Check the circuit around C31, C32 and RV-2. Make sure the 2 zener regulators (D5 and D6) are working properly. Measure their voltages and also measure the output voltage range of RV-2 bias adjust pot. -mgriffin
2475-130 212HD 130 MM
Thanks for your fast reply, I supper appreciate it! Prior to the capacitor replacement - apparently the amplifier was played through. So now after the capacitors have been replaced I am checking each new capacitor. I will in fact go back the area your mentioned and double check everything. Thanks again! Added the schemated I'm using in troubleshooting.
Repaired with caps - Thanks! Quick question about tubes
The 212HD 130 (2475-130 with a 12AX7) is now working. I am thinking about replacing the original Sylvania 6CA7's with a matched quad set of JJ E34L's. Everything I am reading in reference to the to the amps high plate voltage I understand the bias should be set lower. What would be your opinion on the level for tube protection? I am using a Bias Probe that has been a good quality through all of my other amps in the process. I currently set the bias at the 10 ohm resistor to .5vdc after the repair. now considering a tube replacement to E34L's. I have experience with Fender's and Marshalls, but this is the first Music Man I have had, I sure do appreciate connecting with others experience! Thanks Again. Paul
That old 1/2v at point y won
That old 1/2v at point y won't cut it in today's world of junk tubes. I personally would put some one ohm resistors from the cathode to the 10 ohm and directly read the voltage across the one ohm resistor, giving you an accurate reading of EACH TUBE. Reading the sum of the volage is not going to do you any good if you have one tube hot and another one cool. You are going to get a total voltage that way. Today's tubes are way too flaky to handle that way. JMHO. Mike. PS- I'd set them at 21-22ma draw (MV) or even a tad lower.
N/S C007943 restored with two EV speakers
great sound !
Direstrat
Looks Good too!
Looks good too!
Good news
Hello,
I recommend this video : https://www.youtube.com/watch?v=uyn080vOA34
a second part is being filmed. Thank's to Philippe !
As for me, I will be back soon with a new MM 130HD212 : N/S C003246 !
The N/S C007943 restored with two EV speakers in action : https://www.youtube.com/watch?v=JRALykaLq2A
Have a nice day !
Dire Strat
Hello
Hello
The N/S C003246 on the workbench : https://www.youtube.com/watch?v=xjwzHXLA_eQ
An full original and early model in mint condition : The 2-130-E PT is here and the famous 12 AX-7 too : The 12AX7 provide gain and phase splitting. Without proper cooling the EL34's would overheat and fail. Tom Walker designed also a class B drive circuit, which used LM1458 and JE 1692 transistors to drive cathode of the EL34 instead of the original grid drive.
Have a nice day !
Direstrat
The N/S C003246 on the workbench : asymmetrical saturation
Hello
I had in mind that an asymmetrical saturation was linked to the imbalance of the push-pull...
After resolving the big saturation that appeared (after bias calibration) on the negative waves at the power stage linked to the approximate matched quad EL34 by replacement with a quad EL34 re-matched with my own tube-meter (currents at the anode which do not differ more than one milli-ampere at the saturation limit) : But after a few measurements, it was - it seems - not the only reason in the end : By taking measurements on each stage of the sound signal (measurements at the output of each LM307H in preamp at first, then of the driver and finally of the phase inverter), I was also able to observe an asymmetrical saturation of the phase shift stage therefore on the second triode of the 12AX7 mounted as a cathodyne while the stage driver did not saturate himself (first triode of the 12AX7) :
https://youtu.be/4j9mYteUMhg
Have you meet this asymmetrical saturation on the cathodyne 12AX7 triode ? I probably must design new R57, R52 and R53 values ...
An 130HD head (N/S A000894) and the C002697 and C002635 will arrived too on my collection !
Have a nice day !
Check Power Supply
Check the low voltage power supply voltages + and - 16V. If one fails, signals will get clipped. -mgriffin
asymmetrical saturation
Hello Mike !
Thank's a lot for your expert advices. I will re-check the LM307H power supply but at first check, no problem with the main board signal output. The asymmetrical saturation was linked to the second triode of the 12AX7 : the phase inverter. Unless I am mistaken, the cathodyne phase inverter brings absolutely no gain, this being always slightly less than unity. On the other hand, the impedances are significantly different depending on the anodic and cathodic outputs. These impedance differences also affect the respective bandwidths on the anode and the cathode. The cathode is brought to a high potential. It is therefore necessary to bias this stage accordingly. I wonder about the polarization of this stage.
Have a nice day
130HD head (N/S A000894) checking
Hello,
A new piece of my MM amp collection seems to be restaured : I must recap the dog house and the DB2 circuit seems to be instable. So I will take care of this master piece ! Let's go !
Have a nice day
Direstrat
130HD head - Driver Board DB2
Hello
The output signal from this original DB2 circuit present some instable saturations. The 150 microF 50V capacitor, the "vintage PVC6147 Mallory" 47nF 600v Brown capacitor and two Carbon Composite resistors must be changed... So i take advantage of this situation to process a complete DB2 reconstruction.
Have a nice day
Direstrat
DB2 eyelet board rebuilt
Only a new color !
Have a nice day
Direstrat
DB2 eyelet board rebuilt
Hello,
With some new electronic components !
Have a nice day
Direstrat
Not criticizing here but
Not criticizing here but curious why you built a new one and didn't just fix the old one! Mike.
Hello Mike !
Hello Mike !
Thank's to read my post. Good question, especially since my philosophy is to fix the old one as much as possible !
In this case, the eyelet board was so damaged by the overheating of the electrolytic capicitor and two resistors that I prioritized safety by completely rebuilding the DB2 circuit, especially as one of the legs of the destroyed capacitor and one of the damaged resistances are through the eyelet board and provides the connection under the board which is seriously heated !
Another cool reason is to prove to myself that I can completely rebuild one of the best guitar amps in the universe if needed !
Now, my DB2 rebuilt eyelet board seems to be a good spare with the right color ! ;-)
Have a nice day !
Direstrat
Rebuilt DB2 eyelet board installation
Hello
In the right place !
Have a nice day
Direstrat
Rebuilt DB2 eyelet board is... Ok !
Several tests... and grid bias calibration... before the final test : Playing music !
Have a nice day
Direstrat
Neon : amber or red ?
Hello,
The MMs neon that got sunburned turned amber... Let's leave room for the original color !
Have a nice day !
where the light is
It would be a red one !
Music Man 130HD212
My private collection at this day.
Have a nice day !
Dire Strat
Pretty darned nice!
Pretty darned nice!
Wow!
Yes indeed. A very nice collection.
Thank's
That's only a part of. And I can tell that each one has their own tone !
Have a nice day !
Dire Strat
What's the chassis sitting on
What's the chassis sitting on the Peavey?
212HD130 chassis
Hello
It's a 2475-130-EX second generation. The maintenance of this magnificent amp was executed in a dramatic manner !
So I decided to give it a restoration worthy of it.
Have a nice day !
Dire Strat
WOW! The hot glue is a touch!
WOW! The hot glue is a touch! I've used the leads to solder to but I always scrape and hog tie them BEFORE I solder for more mechanical adhesion. Somebody didn't want to do ANYTHING right. Can't see the rest of the chassis guts well enough to see any more globs! Good luck! Mike.
hell of glue
Hello,
the hell of glue has destroyed all hope of recovery of the dog house's fiberboard... So rebuilding seems to be the cleaner process...
Have a nice day !
Direstrat