Amp issue - help needed please!
Moderators: Slowy, Capt. Black
-
- Vintage Post Junkie
- Posts: 2763
- meble-kuchenne.warszawa.pl
- Joined: Fri May 21, 2010 10:08 pm
- Has liked: 8 times
- Been liked: 251 times
Amp issue - help needed please!
So slightly weird issue with the Calvin v3m I picked up.
Bad hum unless I pull the input lead to a side (hum then goes away until I release it). Hard to play while holding lead in that pose
I expect there’s an issue with the input jack but that seems likely to be a PITA to get to?
I’d add a video but don’t know how to do that.
Bad hum unless I pull the input lead to a side (hum then goes away until I release it). Hard to play while holding lead in that pose
I expect there’s an issue with the input jack but that seems likely to be a PITA to get to?
I’d add a video but don’t know how to do that.
- NippleWrestler
- Vintage Post Junkie
- Posts: 2946
- Joined: Sat Jan 02, 2016 5:05 pm
- Has liked: 81 times
- Been liked: 1079 times
Re: Amp issue - help needed please!
Take out the PCBs and have a look. I don't think you'll be able to repair anything from the outside and I suspect the ground connection isn't as reliable as it should be.
-
- Vintage Post Junkie
- Posts: 2763
- Joined: Fri May 21, 2010 10:08 pm
- Has liked: 8 times
- Been liked: 251 times
Re: Amp issue - help needed please!
Ok that’s been helpful. I’ve opened up the amp. I can see that when I pull the lead to the side the sleeve is touching the metal in the hole which results in ground being connected. But it seems that ground is not connected the proper way ie through the socket.
Here’s the socket. From my limited electronics knowledge it appears that the signal is meant to ground via this yellow capacitor 224J63 (based on tracing the signal route from sleeve connector in the socket through to the ground connection to the chassis). But the capacitor is giving me a nil reading on my multimeter’s capacitance and resistance settings.
I’m thinking the capacitor is toast. My questions:
1. Where am I going to get one of those to replace it?
2. What is its actual purpose in the signal route to ground? (Google tells me it is a 0.22 uF film cap)?
Here’s the socket. From my limited electronics knowledge it appears that the signal is meant to ground via this yellow capacitor 224J63 (based on tracing the signal route from sleeve connector in the socket through to the ground connection to the chassis). But the capacitor is giving me a nil reading on my multimeter’s capacitance and resistance settings.
I’m thinking the capacitor is toast. My questions:
1. Where am I going to get one of those to replace it?
2. What is its actual purpose in the signal route to ground? (Google tells me it is a 0.22 uF film cap)?
- Attachments
-
- IMG_3042.jpeg (2.39 MiB) Viewed 109786 times
- jeremyb
- Chorus of Organs
- Posts: 41471
- Joined: Sat Dec 06, 2008 9:03 am
- Has liked: 7837 times
- Been liked: 4227 times
Re: Amp issue - help needed please!
Capacitor sourcing wise: https://www.jaycar.co.nz/220nf-630vdc-p ... r/p/RG5222
I'd be tempted to replace that jack, jaycar have those sockets too: https://www.jaycar.co.nz/high-quality-p ... k/p/PS0195
I'd be tempted to replace that jack, jaycar have those sockets too: https://www.jaycar.co.nz/high-quality-p ... k/p/PS0195
Slowy wrote: That's the problem; everything rewarding is just such hard work. Regret takes much less effort.
- NippleWrestler
- Vintage Post Junkie
- Posts: 2946
- Joined: Sat Jan 02, 2016 5:05 pm
- Has liked: 81 times
- Been liked: 1079 times
Re: Amp issue - help needed please!
It's a 220n cap rated for 63v. I have about 100 of them if you get stuck and are in Auckland. Although mine are 100v and a little fatter to reflect this.
Then reflow those solder joints around the jack and you should be sweet. Solder does harden and crack over time.
Then reflow those solder joints around the jack and you should be sweet. Solder does harden and crack over time.
- sizzlingbadger
- Vintage Post Junkie
- Posts: 8304
- Joined: Sat Jan 15, 2011 7:12 am
- Location: Wire Wrapper
- Has liked: 1218 times
- Been liked: 1408 times
Re: Amp issue - help needed please!
It won't be grounding through the cap. I would just re-flow the solder joints on the board and clean the contacts in the jack first.
"Revolt Against the Solid State"
- NippleWrestler
- Vintage Post Junkie
- Posts: 2946
- Joined: Sat Jan 02, 2016 5:05 pm
- Has liked: 81 times
- Been liked: 1079 times
Re: Amp issue - help needed please!
Presumably that's C106? That goes between lugs 2 and 3 of the jack.
According to Aiken amps it's there for added protection against noise/interference:
"...Fortunately, there is a simple addition to the star ground scheme that will make for a very quiet amplifier with no RFI. Simply add a 0.01uF capacitor from the chassis to the ground lug of the isolated input jack..."
Although 10n to 220n is quite a big difference.
According to Aiken amps it's there for added protection against noise/interference:
"...Fortunately, there is a simple addition to the star ground scheme that will make for a very quiet amplifier with no RFI. Simply add a 0.01uF capacitor from the chassis to the ground lug of the isolated input jack..."
Although 10n to 220n is quite a big difference.
Last edited by NippleWrestler on Mon Jan 08, 2024 9:50 am, edited 1 time in total.
- sizzlingbadger
- Vintage Post Junkie
- Posts: 8304
- Joined: Sat Jan 15, 2011 7:12 am
- Location: Wire Wrapper
- Has liked: 1218 times
- Been liked: 1408 times
Re: Amp issue - help needed please!
And the cap will show as shorted when there is no input jack as the connections will be closed.
"Revolt Against the Solid State"
-
- Vintage Post Junkie
- Posts: 2763
- Joined: Fri May 21, 2010 10:08 pm
- Has liked: 8 times
- Been liked: 251 times
Re: Amp issue - help needed please!
This is the now removed cap. If I test it using my cheap jaycar multimeter it gives no reading (neither short nor anything).
It is C102 on the board and the schematic I’ve looked at for the V3M. I think it goes from lug 1 (sleeve?) to c102 to QC2 ground which is consistent with both the schematic and what I see physically.
It is C102 on the board and the schematic I’ve looked at for the V3M. I think it goes from lug 1 (sleeve?) to c102 to QC2 ground which is consistent with both the schematic and what I see physically.
- Attachments
-
- IMG_3043.jpeg (2.02 MiB) Viewed 109718 times
- RectifiedAmps
- Fender
- Posts: 509
- Joined: Tue Jul 22, 2014 7:05 am
- Location: Wellington
- Has liked: 204 times
- Been liked: 240 times
Re: Amp issue - help needed please!
Can you post a photo of the underside of the input jack pcb? It would help to see the solder pads and the circuit traces.
It would be unusual for the virtual ground cap to be a problem (first time for everything though) and it sounds more like a problem with the jack itself - either it needs resoldering or the tension isn’t right so the ground tab isn’t touching the sleeve of the cable plug, which means it needs replacing.
Remember that the ‘ring’ and ‘sleeve’ of the jack are connected when you insert a mono plug. Sometimes the ring is wired to a muting circuit and the sleeve is a standard ground, to keep the amp silent until a jack is inserted.
It would be unusual for the virtual ground cap to be a problem (first time for everything though) and it sounds more like a problem with the jack itself - either it needs resoldering or the tension isn’t right so the ground tab isn’t touching the sleeve of the cable plug, which means it needs replacing.
Remember that the ‘ring’ and ‘sleeve’ of the jack are connected when you insert a mono plug. Sometimes the ring is wired to a muting circuit and the sleeve is a standard ground, to keep the amp silent until a jack is inserted.
- RectifiedAmps
- Fender
- Posts: 509
- Joined: Tue Jul 22, 2014 7:05 am
- Location: Wellington
- Has liked: 204 times
- Been liked: 240 times
Re: Amp issue - help needed please!
Here’s the input part of the schematic. I was wrong about the ring - it does nothing. But I still think the jack is your most likely suspect at this stage.
-
- Vintage Post Junkie
- Posts: 2763
- Joined: Fri May 21, 2010 10:08 pm
- Has liked: 8 times
- Been liked: 251 times
Re: Amp issue - help needed please!
Thanks for the help. I replaced the cap and touched nothing else on the basis that the less I touch, the less I might break! But seems to be fixed now
- sizzlingbadger
- Vintage Post Junkie
- Posts: 8304
- Joined: Sat Jan 15, 2011 7:12 am
- Location: Wire Wrapper
- Has liked: 1218 times
- Been liked: 1408 times
Re: Amp issue - help needed please!
That is odd, I wouldn't expect the cap to be an issue, maybe just unplugging the board has cleaned the connectors and now its ok.
"Revolt Against the Solid State"
- jeremyb
- Chorus of Organs
- Posts: 41471
- Joined: Sat Dec 06, 2008 9:03 am
- Has liked: 7837 times
- Been liked: 4227 times
Re: Amp issue - help needed please!
Great outcome regardless!
Slowy wrote: That's the problem; everything rewarding is just such hard work. Regret takes much less effort.