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Messages - Tassieviking

#1
Thanks guys for the answers, I think I will not keep the Electrolytic caps since I don't know the age of them.
Better be safe then sorry.
#2
Have you tried making your own PCB?
I like using KiCad to make up PCB's for whatever I want to build, I get 5 PCB's from JLCPCB for the price I can order one from someone else.
If you download KiCad you should be able to check out the PCB I made for the Sunn Beta, my design is adaptable for the Bass or Lead version, just install the right components.
I guessed at the spacing of the pots so they will not match the original amp, but close enough for me.
Look up: https://www.ssguitar.com/index.php?topic=5080.msg39729#msg39729

I think I left all the files there, including the Gerber files I sent to JLCPCB when I ordered my PCB's
If you want to use my PCB just order some.
I think I have tested the Bass version of my PCB, but not completely sure, I have had a messed up year so far.
#3
Amplifier Discussion / Do Electrolytic Caps Age ?
June 12, 2022, 03:57:08 AM
G'day all
So my father died a week ago,and my brother 3 years ago and mum 5 years ago.
Going through all the stuff in my fathers house I have found lots of Electrolytic caps,
Some are around 6800uF 65V, 2200uF 80V, etc. I know these used to be my brothers but he moved overseas about 20 years ago.
Will they still be ok to use in new amp builds or should I scrap them, they have never been used.
There are also bags full of 1uF, 10uf, 22uF etc, never used and heaps of WIMA box caps.
I have to ship them over 2000km back to my place so I only want to keep good *s!!t*.
???
#4
I always wonder why someone who struggles with English don't put up where they are from, or what language they speak or understand. There is such a diverse group of people  on the forum there might be someone who could explain it in whatever language they prefer.
I can speak some Swedish, Norwegian and fluent in English, I personally don't care if someone replies in another language. I don't think there is a rule everything has to be in English, but an English translation as well would be nice if it solves the problem. Just my opinion, music is universal.
#5
It looks to me like the 2 dots might have been a jumper wire which was removed, and then the earth re-routed with a wire, but I haven't seen the PCB in an Amp.
If you have the amp check what is there originally.
The solder pads must have been used for something.

Found a picture of what I think is the correct link on the other side, I circled the link in red.
#6
Schematics and Layouts / Re: Samick SM-10 Amp
April 30, 2022, 08:26:29 AM
Thanks for all those comments guys, I was only thinking of replacing the Electro-caps and the pots if the school wants them.
I just wanted to make them last as long as possible for the kids.
#7
Schematics and Layouts / Re: Samick SM-10 Amp
April 20, 2022, 11:27:22 AM
Thanks Joe.
I was given this amp and a Marshall G15R-CD for free, apparently the pots are noisy.
I am thinking of giving them to the local primary schools music department if they want them.
I think young kids will like them, as long as the school has some guitars.
I think I will change all the Electrolytic caps and all the pots in both amps before I ask. The amps are 23 and 28 years old I think

Caps and Pots will cost up to $13 total for both amps from Tayda, and I am putting in an order soon anyway. That's if I use the best Electros Tayda has.
I might also mount some speaker cloth across the backs to keep the little fingers out of the speaker. Or maybe a metal mesh would be better.
#8
G'day SemiConductive
I'm fairly new to audio circuits myself, but I have heaps of experience with industrial electronics.
The way I understand the active inverting low pass filter of IC1B is as follows:
The gain is set with R4 and R6(and R5), we don't want to mess with this, unless you feel there is too much gain with the pedal engaged. then increase R5 till you are happy with max gain. (Pot ?)

So R6 is 150k, or 46.78899k with R5 in the circuit.
My understanding is that you calculate this the same as a RC low pass filter.
Capacitance is 470pF
Look at this page, the same formula for normal RC Low Pass filter as an Active Inverting Low Pass Filter like yours. So we can use the top calculator for frequency drop off.
https://www.learningaboutelectronics.com/Articles/Low-pass-filter-calculator.php#answer1

With R=150k and C=470pF you have a drop off frequency of  2.26 kHz
With R=46.78899k and C=470pF you have a drop off frequency of 7.24kHz
If you want 7.2kHz with the R=150k you have to change the capacitor to C=146pF (150pF)

You can easily put in a switch to change the frequency roll off capacitance to set it were you like it, rotary switch you get heaps of otions, but a bit overboard

But maybe I misunderstood the whole thing and got it wrong, If I did can someone please give me a hard smack over the ears please, That way I will remember next time.
Michael
#9
Schematics and Layouts / Re: Samick SM-10 Amp
April 19, 2022, 12:40:31 PM
Quick question for someone, when you change capacitors in an old amp,
do you just change the Electrolytics ? (Preventative Maintenance)

I have only changed the electrolytics in most amp I have come across.
Should I change greencaps and ceramics as well ?

In the 45 years I have been an electrician I never replaced capacitors just because they were old, and I mainly worked in maintenance, Industrial electronics mainly.
Lots of huge DC drives for DC motors, PLC's, big stuff mainly. I also did instrumentation  calibration and testing as well.
Just never any Audio stuff, until now.
Thanks
#10
Schematics and Layouts / Samick SM-10 Amp
April 19, 2022, 12:28:03 PM
I was given a pair of small practice amps last week, one was a Samick SM-10.
I searched the Net for a schematic and some information,-----Nothing----.

I wanted to know what I had before I started re-assembling it, it was pulled apart.
This was the hardest circuit I have ever traced, and strangest for a budget amp.
I have traced it as well as I can for now, but I think I will do it again in the future just to see if I can find any faults in my tracing.

It has a strange setup with the Volume pot and Overdrive Pot.
I have no clue yet what the Overdrive Socket does, when I get it working I will try shorting it out to see if it kills the Overdrive I think.
Serial Number is 94060140, 1994 model ?

Here is the schematic I have traced at this moment:


 
#11
The Schematic on https://www.schematicsunlimited.com/e/epiphone seems a little bit clearer.
Look for the "epiphone regent 2050r" file.

https://www.schematicsunlimited.com/e/epiphone/epiphone-regent-2050r-amplifier-schematic

This is a good place for finding schematics.
#12
Ops...sorry if I raved on a bit too much in my last post about earthing.
I hope I didn't offend Enzo or anyone else here.
I guess I am a bit sensitive about safety when it comes to electricity.
I have had to revive work mates after getting zapped, not a nice thing.
#13
Some quick reading, and playing with the calculator will help to understand maybe ?
https://www.learningaboutelectronics.com/Articles/Low-pass-filter-calculator.php#answer4
There are several calculators on this site for easy learning, just have to look hard for them.
Another good place to learn:
http://sim.okawa-denshi.jp/en/opampkeisan.htm
http://sim.okawa-denshi.jp/en/Fkeisan.htm
#14
Quote from: Enzo on April 11, 2022, 12:54:41 PMIf double insulated, no need for earth.   Just my opinion.

I don't think I have ever seen a guitar amplifier that is in a plastic box, with plastic pot shafts and knobs.
I think any older amplifier, especially  from the last century, should be earthed if at all possible.
When an appliance is directly connected to your body (strings), there is a potential of electrocution.
Even if the appliance in question (amp) is correctly manufactured we don't know who has modified it, or used the correctly rated parts in any repairs made to it.
Not all power transformers have the right insulation between the primary windings and the secondary windings, when a transformer malfunctions it can short the mains voltage to the low voltage rails and then you end up doing a weird little dance if you are on the other end.
Thankfully it only hurts until you pass out.
I could rave on about the "handy man" installed power outlets I have come across in the last 45 years working as an electrician, how I have seen someone use a wire coat hanger as cable to connect a second power point beside the first one, or thin speaker wire,etc.
I must have found dozens of power outlets where the neutral and earth wires have been swapped, or active and neutral swapped.

Anyway, if it has a metal chassis then I earth it, if any metal you can touch is connected to the circuit (like guitars, microphones etc) then earth it.

If I was a performing artist I would carry a small power point tester with me, and I would most likely have an earth leakage protecting plug on the lead to my amp, and any other equipment that plugged into a power outlet.
At least in Australia you can get plugs that will protect against electrocution that you can fit on the end of a power lead.
#15
Here is a crazy thought Jimi, what if you put the 5010 amp and the 5205 amp side by side, and wired the pre-amp of the 12 watt reverb to the power amp of the 30 watt ?
Go from pin 1 of IC2 of the 12 watt and go to C8 of the 30 watt.
Just to see how it would run with the 30 watt amp attached to the 12 watt pre-amp.
I think I will just make a picture up so it is easier to understand. =)