UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Mullard 5-10 amplifier

Diabolical Artificer · 12th Jun 2019, 6:32 am

Lot's of possible fixes reccomended there but for a start find out where this 100hz (from your oscillogram) is getting in, BTW what is the amplitude, couldn't see what your volts/div was set to.

Get your scope and check the input to V1, then V1's anode, but check your scope can handle how many volts are on V1 anode, then go through the rest of the amp systematically. Tack a 630v 0.1 or similar cap onto anode pins if anode voltage exceeds scope Vmax in. Your right a PP OP stage should reject common signals, but only to a point.

You could also pull out the ECC83 and power up briefly to check which bit of the amp the 100hz is sneaking in. for more details on the 5-10 see here - http://www.r-type.org/articles/art-003e.htm

Andy.

12th Jun 2019, 6:32 am	#24
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,669	Re: Mullard 5-10 amplifier Lot's of possible fixes reccomended there but for a start find out where this 100hz (from your oscillogram) is getting in, BTW what is the amplitude, couldn't see what your volts/div was set to. Get your scope and check the input to V1, then V1's anode, but check your scope can handle how many volts are on V1 anode, then go through the rest of the amp systematically. Tack a 630v 0.1 or similar cap onto anode pins if anode voltage exceeds scope Vmax in. Your right a PP OP stage should reject common signals, but only to a point. You could also pull out the ECC83 and power up briefly to check which bit of the amp the 100hz is sneaking in. for more details on the 5-10 see here - http://www.r-type.org/articles/art-003e.htm Andy. __________________ Curiosity hasn't killed this cat...so far.