Hallo !!

Ich bin fransoze und ich spreche deutsch nicht gut. Also, ich versuche im englisch

I'm studying MB DR schematics for some weeks in order to understand all parts and to build one soon.
I've got different schematics but use espacially this one : http://www.tube-town.de/diy/dual_rectifiers/mesa_boogie_dual_rectifier_schematic_original.zip

some questions didn't find any answer yet :
- the LDRs in the switch matrix section : where can I found them and what can I use ? (reed relays ? ...)
- there is two switches : RLY1 et 2  (FX bypass and clean / disto selection) --> what are there ? what can I use ?
- same question with the S9 switch fot channel cloning
- how does the switching matrix work ?

about the power section :
- the bias supply : HOW can we make a -51 bias voltage supply with only the 50 AC supply ? I'm studied electronic and there is something I can't understand in this.
- the power transformer : I think I should take the Hammond power transf 373BX. what do you think about it ?
- the output transformer : I choose the hammond 1650T. 120 W is better than 100 W isn't it ? in order to not distored the output signal !
- but : Is the output impedance of this transformer ok for a MB Drecto ? I couldn't find any information about the original one

THX in advance for all the information you can give me !
let's rooock !!!

tschüss !!!

Sermac

I had not much time to study all your schematics, but the
+/- voltage you get with the two single rectifing Diods D9 and D10.
You know AC? It got positive and negative wave, positive wave passes D9 negative wave passes D10. With the el-capacitor to the ground you have +/- Voltage.

thx but I really know what is AC and how the bias supply chaine works.

I notice that my question wasn't well written :

We've got 50 V AC from the transformer
D9 gives you negative supply
but, as I know, the system is totally passiv, with resistors and capacitors :

How can we get less than -50 V DC for the bias supply ?

I made some simulation of the circuitry and I can't find a way to get - 51 !!!

Hi,

maybe your simulation works with effective voltage Ueff so you need to config the sourece with
Umax~=Ueff~* SQR(2) -> 50*1,41
Umax~= 70,71 Volt

What program do you use to simulate?

Hallo

my simulator is PSpice in its student version !!

maybe you're right
maybe my componant models aren't good enough too

I don't know if to fixe bias supply is the best solution
mesa made that only because customers should use mesa tubes which need -51 V (6L6)
but if you put an other reference :/

I've got headaches with relays
I've searched for the LRDs ...5Cx but first af all, I've found only 5C1 for 10 $ each
and nothing else 
do you know where I can find some ? or maybe an alternative for those component ?

best regards

Hi,

the most use a LED and LDR in a "heat shrink tube".
Its much cheaper.
I use:
LED 5-9000 WS
A906013

Take this both names an copy on www.reichelt.de into the search field.
You get the price, partpics and can download the datasheets.

here is a picture from someone how made this way

Hi

Did you already use the LDR?

500k or at least 1,5M Ohm Off Resistance is far away from what you need to mute a Channel.

cu

thx for idea !!

"500k or at least 1,5M Ohm Off Resistance is far away from what you need to mute a Channel."

I'm afraid of that... I'll investigate this data

Hi all

Does some one use Orange drops capacitors ?
what do you think about it ? about he sound ?

Do you know if the prices on TT online shop are for one cap. or for 5, 10 ... ?

thx

The Price is for 1 piece.

Orange Drops are good Capacitors, but you can also use Wima MKP10 or others.
The thing that counts ist the dielektrikum (Polypropylen), not the name on the package

cu

you're right

but I've heard that the best capacitors for guitar amps are MKC ones.

But there are difficult to find in all values...

After that, you have different performance between different MKP capacitors, as orange drop 715 and 716 (716 are the better for high end audio amps, that what is said in books )

so I think I'll take some orange drop, as fender does

Hey Guys,
I think wima ,not shure what type especially,are the best for cheap money!Look at the datasheets and read why.
Best regards
                     Max