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Author Topic: Soldano sp77 earth problem? also how do you dial your poweramp  (Read 34773 times)

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gb

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Normally you should be able to see cracked solder joints.

Thanks mate. I will definately try this also to make sure. The tube sits quite loose in the socket compared to the others which are firm
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rnolan

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Hey gb, might be good to put in a new tube socket ?, they should seat firmly with good contact, not loose, the socket pin receptors may have pried apart so you may be able to nudge them closer again ? but in the end the tube should sit firmly or the contact will be intermittent.
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gb

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Thanks mate. Yes im thinking ultimately I will change the socket or have someone do it for me.. im sure I can manage this. Where is the best place ti buy quality tube socket parts? In australia
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rnolan

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Hey George, not sure but a friend of mine may know.  These guys in Qld have sockets (http://evatco.com.au/product-category/sockets/) and is where I bought the Mullards for my 2 MP2s.  Nice people, reliable etc and know their stuff, reasonable prices for tubes. Give them a call, maybe send them a photo in email of what you need. Does the schematic say what socket type you need ? I'm not particularly experienced here, MJMP/Sparker territory.  But my friend is a tube nut, he's due home soon so I'll see what I can find out for you.
Cheers R
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MarshallJMP

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If you can't find i can send you a few sockets with gold contacts,these don't tarnish.
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gb

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Thanks guys.. !!
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gb

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Can I ask an electronic question. I can mod my sp77 to sound like an x88r. Below are the steps:

You can make it sound very close to an X88R by putting a 1uf in parallel with R22 (SLO has this.)A SPST switch to ground added to R9 gives you a clean/crunch option on green.A SPST switch via 15k resistor connected in parallel to R17 gives you a big gain boost .

I can easily do the 15k resistor mod. But the 1uf mod im unsure. I went and bought 2 1ufs which are capacitors but the mod says to connect a 1uf to R22 which is a resistor... saying that I understand the capacitor has a - and + side which is marked so how would I know which way to do this.. also I have 2 different voltage rating 1uf.. a 53v and 430v or there abouts.  How do I know which one I would need to use?

Any help would be appreciated.  They are easy mods to perform just need some clarification.  I tried  emailing soldano with no response.. the above is their mod.
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rnolan

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Hey George, I'd go with the gold sockets from MJMP !!!, replace them both.
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MarshallJMP

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Do you have a schematic of the soldano so i can take a look?
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gb

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Do you have a schematic of the soldano so i can take a look?

this is one i found online that has the Resistors labelled as per the circuit board



and here is the official schematic

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gb

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ok pretty proud of myself.. i went through and checked EVERY resistor (youtube showed me how). Each resistor measured pretty close to its rating which i used the above schematics as reference to values when tested on the board except the following:

-R2 suppose to be 1M but mine read 0.01 so i pulled it off the board and tested as 1M so assumed in the circuit causing this?
-R9 which is suppose to be 100K but mine read 87K. I pulled it off the board and it was fine so i assumed in the circuit is causing the drop.
-R10 is 1M resistor but mine reported .76M, after R9 i assumed the same thing but didnt pull it off the board.
-R35 1K but mine was .988 ..again i assumed the same

The rest were spot on.

so i found R24 was dead .. i changed it out and HELLLOOO nomore funny buzziness the preamp came alive. now the only issue is it has very low output as in the output is all the way up and the gain all the way up and its barely audible with the power amp cranked (bedroom volume is the best way to describe it) so something is wrong still and not sure where to check, also there is a loud hum that increases with volume on either preamp or power amp (not power amp its the preamp) (even with amp separated from rack and not touching metal or anything else.) .. perhaps these 2 issues are related? i remember when it was working in all its glory it was quite loud and output only needed to be on a few notches with the power amp cranked.. now its nowhere near that with output cranked on preamp.

Marshalljmp are you able to advise based on the schematics what i could check that might cause low output..? i havent tested capacitors. A guy at the local electronics store said with audio gear to check capacitors.. or a ground issue?

Im nearly there! soldano havent replied to any emails so i gave up and considering the circuit board looks simple with a few resistors and capacitors i feel with some guidance i could fix this issue myself. ive learnt heaps in the process.


Cheers
« Last Edit: Time Format by gb »
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MarshallJMP

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Can you measure the anode and cathode voltages?
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gb

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Can you measure the anode and cathode voltages?

i can if that can be done with a multimeter.. haha and how do i do that? you will have to tell me where exactly to put the multimeter probes on the board

ps ill also add all these issues started about a week after I sprayed contact spray on the V1 tube socket to rectify scratchiness (which is fixed now) . i wonder if this has caused something? ive tried to clean as much as i can of it off the board
« Last Edit: Time Format by gb »
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gb

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now saying all that i just tried another new resistor (this one was different coloured 5 band as opposed to the previous 4 band) 100K for r24 as per the schematics and now the preamp is quite loud .. back to normal!!!

im not sure about the bassy hum but the noise gate cleans it up. i think ill leave it for now but will take it to a tech to check out in future if its still an issue..

how funny though changing that same resistor to another same value one just fixed it up!

thanks Marshalljmp for checking out! wow a 0.50c resistor all it was, and i nearly (literally this week) was going to send it to a tech.

*******************

ok next question. Can i put an input jack to the rear of the preamp. And is it as simple as duplicating the front jack but to the rear (IE run some wires from the solder points to the same pins on the rear jack?)

i love how the ada has the rear input for rack stuff and because i plug my guitar into the decimator at the rear
« Last Edit: Time Format by gb »
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rnolan

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Hey George, (Can i put an input jack to the rear of the preamp. And is it as simple as duplicating the front jack but to the rear (IE run some wires from the solder points to the same pins on the rear jack?) ), Yes  :thumb-up: , just like many (older) amp inputs, the input jacks are mostly in parallel.
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