Melbourne Daughterboard for M2X

[zman01]

Yes X, I made a bit of progress on the Melbourne’s this evening.

Hi Vunce,

How is your build coming along?

 

[Vunce]

Hi Zman!
It was going great until last night, a tiny solder bridge on the Yarra MB stopped me in my tracks
Two working Melbourne’s turned into zero.
Troubleshooting and repair tonight

 

[zman01]

Vunce,

Sorry to hear that and I hope that you get it sorted out real quick.

 

[Vunce]

Thanks Z,
I hope so too! You know how these situations can go, definitely need some Metallica background music for this one

 

[xrk971]

Yes, “Nothing Else Matters”

 

[Vunce]

Exactly X
My whole work day was thrown off because of this....

 

[batty]

I see that 2 resistors are mounted off the board on lugs, can this be done with the component legs instead of the lugs?

 

[batty]

I have 2 boards built now less the 2 transistors and the 2 resistors on lugs. It looks like I need to read all the posts to find out why the lugs and what the gain is (4.7?).

 

[xrk971]

You don’t need the lugs. Just insert directly into the holes/pads. The default gain is 15.6dB and is set by the (R118+R119)/R118 value of (5k6+33k)/5k6. If you want 30.6dB if gain use 1k for R118 etc. leave R119 at 33k.

Add some resistor lead clippings to the two test points to measure bias current though.

I think JP added feb lugs to allow easy de-soldering and exchanging of the gain resistor.

 

[xrk971]

Hi Zman!
It was going great until last night, a tiny solder bridge on the Yarra MB stopped me in my tracks
Two working Melbourne’s turned into zero.
Troubleshooting and repair tonight

Hi Vunce,
How is the trouble shooting going?

 

[Vunce]

Hi Vunce,
How is the trouble shooting going?

Hi X,
The solder bridge was fixed quickly. The Melbourne’s were another story. I’ll give the short version though. After spending several hours checking/testing every component, the problem turned out to be faulty meter lead!!! The Melbs are all good

 

[xrk971]

That’s great news to hear, Vunce. Sorry you were another victim to the bad wire Gremlin. That must be very frustrating - but hopefully a new page has been turned.

 

[Oracle1]

Instead of BC557B can i use BC560C ?

 

[xrk971]

Yes, that's fine.

 

[batty]

Does this build have gain? Is it the correct version for the Yarra?
1 more dumb Q, what is the part number for the heatsinks, I have some clip on ones but they are too large, TO126 right.

 

[xrk971]

Default gain is 15.6dB. The gain is set by R119 and R118.

Gain = (R118+R119)/R118 leave R119 alone at 33k and adjust gain via R118.

 

[batty]

TY, I want the Yarra Pre to drive my M2x, hoping it will be a good match as my Mesmerize is unity gain and is really not enough, great sound though.

 

[gary s]

Hi batty, RS - Online here in OZ has the Fischer SK95-25-SA-220 heat sink in stock (their part number is 189-8319) and they are $3.77 AUD each incl. GST with 23 in stock for next day delivery. That is where I got mine from and are the same ones as shown in the original PCB build photo's.

 

[xrk971]

Mesmerize is unity gain

With 15.6dB and 15.6dB of M2X, you have about 31dB overall which should be perfect for driving with a cellphone or usual RCA source.

 

[batty]

Hi batty, RS - Online here in OZ has the Fischer SK95-25-SA-220 heat sink in stock (their part number is 189-8319) and they are $3.77 AUD each incl. GST with 23 in stock for next day delivery. That is where I got mine from and are the same ones as shown in the original PCB build photo's.

TY Ordered.