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Messages - tonyharker

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Amplifier Discussion / Re: Heatsinks for your poweramp
« on: December 10, 2017, 12:57:54 PM »
The LM386 is not an op amp but a power amp, albeit low power.  It could be getting hot because it it is oscillating. It should be cool if it is idling ie not passing a signal.

The Newcomer's Forum / Re: TDA 2030 Guitar amp build oscillation problem
« on: September 26, 2017, 02:17:05 PM »
Can you show us some pictures and the schematic you used?

Instead of that class a amp you might like to look at a chip solution eg. LM1875, TDA2030, LM3875, LM3886.  There's a lot of information about these on the 'net also check out their datasheets - google. Kits and bare PCBs are available on Amazon and even eBay if you want to risk it. The LM1875 although listed at 20w will put out more at higher voltages into 8 ohm speakers.  The boards will be OK even though the IC may be suspect but they are cheap and a good starting place.

First of all your're going to need a humongous heatsink,  then I would use a fet preamp to give you the high impedance needed. Something like the tillman preamp here . change the 51k resistor for a 47k pot for the volume control.
BTW welcome to the forum. :)

If you feel like trusting China you can get TBA810 from both Ali Express and eBay.

If Q8 is blown, then its likely Q5, 6, &7 are as well.  Initially find what caused them to go in the first place.

Amplifier Discussion / Re: TSA15H Broken down ... repair ;-)
« on: April 20, 2017, 05:51:24 PM »
Can you repeat that in English please?

Tubes and Hybrids / Re: blown filtercapacitor in 100watt. Why?
« on: March 01, 2017, 03:00:37 PM »
I expect the electrolyte just dried out, which can happen after a few years.  The ESR goes high it gets hot then BANG!  Checking the ESR of a capacitor is a good test of its health.

Just turn the volume down.

Amplifier Discussion / Re: Quick question about this circuit
« on: June 13, 2016, 05:30:31 AM »
R1 is connected the way it is - is to 'Bootstrap' it via C1 to raise its AC impedance load on Q3 thus increasing the gain without upsetting the DC conditions.  Leave it where it is.

Preamps and Effects / Re: Best simple distortion circuit
« on: May 18, 2016, 12:19:32 PM »
The signal at this point will not be high enough for rectifier diodes to clip. Their forward voltage is too high.  You may get away with germanium diodes however, but you will have to try them.  If they don't work, then its another gain stage I'm afraid.

Amplifier Discussion / Re: Feng - Mini Amp using PAM8403 (2x 3 Watt)
« on: April 14, 2016, 05:31:05 AM »
Does the TL072 work OK at 5v as the datasheet shows a minimum of about +/- 3.5v (7v total)? The TL062 would be better as this shows a supply of less than +/- 2v. The LM358P would also be suitable it has a minimum supply of +/- 1.5v.

The Newcomer's Forum / Re: Building my first cabinet, Please Advise!
« on: February 10, 2016, 03:56:54 PM »
Never heard of a speaker pointing up in the air. Are you sure you haven't got them on their side so that they would point right and left??

Tubes and Hybrids / Re: New Build Power Amp IC
« on: October 30, 2015, 05:51:02 AM »
The LM1875 can be used instead of the TDA, and there is a single supply circuit in the Datasheet for it.

Amplifier Discussion / Re: Vintage amp info and power cord?
« on: May 14, 2015, 02:01:35 PM »
Da Vinci amplifiers were made by Magnatone and they just re-badged their standard models.
The transistor versions were build between 1967 & 1968. 
You may be lucky and find a schematic.
This site may be able to help you

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