Faulty Dynacord PM3600 PowerMax Amplifier Repair

A customer brought in a Dynacord PM2600 Power Amplifier and asked me if I could repair it. Let's find out

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TEST METERS
ANENG AN8009 MULITIMETER
KAIWEETS HT118E MULTIMETER
VC480C+ MILLIOHM METER
MESR-100 ESR METER
XC6013L CAPACITOR METER

TM-902C TEMPERATURE METER
LCR-T4 COMPONENT ANALYZER
FNB58 USB ANALYZER
PCI POST ANALYZER
TL460S PLUS PCI_E ANALYZER
TOOLTOP ET120MC2 SCOPE
FNIRSI 1014D SCOPE
NPS3010W 30V 10A PSU
T12 STATION WITH M8 9501 HANDLE
M8 9501 HANDLE
YIHUA 982 Soldering Station C210/C245
FNIRSI HS-02 PORTABLE SOLDERING C210/C245
QUICK 861DW
PROS'KIT SS-331H

INFIRAY P2 PRO IR CAMERA + MACRO LENS
TOOLTOP ET13S THERMAL CAMERA METER
ET13S MACRO LENS
OPTICAL MICROSCOPE
TOMLOV TM4K AF FLEX
TL866 II+ PROGRAMMER
CH341 PROGRAMMER
NC-559-ASM FLUX

DESOLDER BRAID (I use size 8045)
HX-T100 SOLDER (0.6MM)
ESD-11 TWEEZERS

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Thank you
Richard

[philiphazlehurst]

As already mentioned, a scope, dummy loads and an audio signal generator. A audio signal generator that can generate square waves is very useful for determining the frequency response of an amplifier. It's is then easy to diagnose faults with tone controls/loundness controls etc. I now use a battery powered Tenma audio signal generator that sells for around £50 in the UK. I did start off using a mobile phone app for this, until I destroyed the mobiles audio output when testing an amp.

It's also a good idea to test for DC offset voltage across the speaker terminals before hooking up any speakers (maybe you did this off camera). A faulty output device or similar could leave many volts across these terminals which could ruin your speakers day.

[ElTelBaby]

I Note @ 2:02 It clearly states PM 2600
Not as advertised in the description title PM3600

[onthemudd]

Love your methodical approach to troubleshooting and repair.

[davecasper]

A audio signal trace and buzz it type injector might help locate the faulty section in more detail. I have used it successfully with no schematic type of situations. Reverse engineering and familiarization of the components and the sample circuits with data sheets from manufacturers sample circuits have worked for me many times over. Monitoring the output working back helps divide and concourse so to speak. Ex military battle strategy.

[hernancoronel]

Love this videos Richard! Thank you for your efforts!

[avi]

Hi Richard. I have noted on other channels the technicians will inject different types of waves at various frequencies at the input and they view the output for distortions with a scope

[stefanobettinsoli]

Hi Richard. I worked on many of this big professional amplifiers, and the worst situation is when the problem shows up randomly....
If I may, I would like to suggest you to feed the input with a stable signal generator and perform a long test using a dummy load on only one channel at the time at full power. Till now is a standard way ok? But now the tricky part of my way...
To looking for the random problem, you need to build a little tool. A "vibrating table". Some sort of surface large enough to support the amplifier, suspended on four soft rubber shock absorbers. On the same surface you need to mount an electrical motor. On his shaft you need a "wheel" out of rotational center.
When the motor is running the wheel let the surface shake.
Using an oscilloscope on the output during the shake, at max power, under mechanical and thermical stress, you can finally see some signal spikes or variations...
In my experience this is much better and faster than trying to bend the PCB or nocking it with the screw driver

[sherlockholmes]

I guess you would have to build dummy loads, then put a known signal in and check for distortion on the output. More projects to build I guess Richard. Something tells me I saw a guy using a thing called a sweep generator to do this years ago.😀

[Onkel.Moetrik]

Eddie Aho at kiss analog designed all the power supplies on the international space station as well as working for boing and other defence industries. He probably knows everything there is to know about psu and amplifiers 😅 Eddie is probably the youtuber I have the highest respect for, and if I ever should choose to be a nother person I would probably choose to be Eddie Aho 😅😅😅😅😂

[andymouse]

Very surprised you don't have a 100W 8Ω resistor and a sig gen, still noise hunting is fun ! for a top up on audio stuff I would recommend watching ' John Audio Tech' he's a no frills guy with stacks of audio knowledge....cheers.

[leetucker]

buy dummy load kit from PCB way, nice useful project

[shrikedecil]

"Mr. Carson's Lab" might be of interest. Not primarily for his main focus: Refurbishing even older gear. But instead for some of the tools he builds and outlines. Couple specialty widgets for RF circuits outlined that should be under $100 - or nothing with a good parts bin. One of his most recent repairs and refurbishments was also a high-power dual amplifier ... with vacuum tubes.

[janakapriyadarshana]

Hi richrad, nice work, we would like to learn micro controller communication theory with practical

[esbenarndt]

Why not use the schope on the outlets?

[jct]

You already have a scope, what you need is home built dummy load as @Dutch-linux described and an audio signal generator, even a mobile phone app will suffice.

[GapRecordingsNamibia]

What I would say is, if the customer is in close ish proximity go to him and hear what he is talking about in his normal It might not even be the amp that is at fault...

[stillasgoodasnew]

Hello do you take on repairs? If so I have extech multimeter and a extech amp clamp. Cheers

[insaf]

Sir i have sansui 11000 integrated amplifer long time not used not work want help ....how repair....i m from india thank you

[hicks_dwaynes]

Hello, help me please, i need dynacord pm 502 circuit