Question about Kenwood VR-407 Receiver

2 Answers

Kenwood basic M2 Amp Lightning strike

A lightning strike took out a nearby transformer and now my kenwood amp will blow one of the internal 7 amp fuses if the power is turn on to it. The local shop took a look and said that this amp has very strange circuitry and they couldn't help me. Another shop said that the output transistors were all blown but did not know where to get parts. I found a source but they are about $50 apiece and there are 8 of them. It still sounds odd to me that all 8 would be damaged as I believe that this amp has two rails of 4 transistors each, with 4 of them coming on line only at very high settings. The amp was off at the time of the lightning strike. There is no physical damage apparent to the transistors or the heat sinks that they are mounted to. Any ideas? Thanks ratmoul

Posted by on

2 Answers

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 20 achievements.


    An expert that got 10 achievements.


    An expert that got 5 achievements.

  • Master
  • 1,512 Answers
Re: Kenwood basic M2 Amp Lightning strike

You can check the output transistors for short circuits with the low ohms range or diode checker . If they have failed, then it is often a good idea to replace all as much stress can be placed on an output array in this type of failure. to repair reliable, all outputs on an offending channel should be replaced.

Make sure the fuse you replaced was the same type of fuse. check markings.... T stands for sloblo... a fast blo duse may let go at turn on. The power supply may have a shorted rectifier diode in it also.

be aware however, every time a fuse of that rating blows... more damage may be occurring to the amp.

Posted on Dec 15, 2007

  • Level 1:

    An expert who has achieved level 1.

  • Contributor
  • 2 Answers
Re: Kenwood basic M2 Amp Lightning strike

It might be easier for a novice to find the emitter resistors (white rectangular ceramic with three pins exiting) there are four of them
each is a pair of resistors @0.22 ohm each side.
Connect a multimeter to the center pin, and each outer pin in turn,
if you find an open circuit in any of these then the respective output transistor has failed (shorted to the power rail + or - depending on whether its a NPN (positive rail) or PNP (negative rail) device that`s failed. As explained above, you will probably need to have the low power pre-drivers replaced as well as this amp is DC coupled,
I have found current limiting resistors in the signal path tend to protect the first and second stages from damage, including the input differential pair.

Posted on Jan 30, 2014

Add Your Answer

0 characters

Uploading: 0%


Complete. Click "Add" to insert your video. Add


3 Points

Related Questions:

1 Answer

I have a kenwood Auto video surround receiver DR / 409 how to reset it

PDF]KRF-V8030D VR-409 - Kenwood
VR-409. INSTRUCTION MANUAL. KENWOOD CORPORATION. B60-4593-00 (EN) ...on the country and sales area. AUDIO VIDEO SURROUND RECEIVER ...

Kenwood VR-409 Manuals > Brands > Kenwood Manuals > Stereo Receiver
View online or download Kenwood VR-409 Instruction Manual. ... Kenwood Instruction Manual Audio Video Surround Receiver KRF-V8030D VR-409.

Kenwood VR-409 Receiver Repair Questions, Solutions ... > Forum > Audio & Video Receivers > Kenwood
Recent Kenwood VR-409 Receiver questions, problems & answers. Free expert DIY tips, support, troubleshooting help & repair advice for all Audio & Video ...

Kenwood VR-409 PDF Owner's Manual Download & Preview > Kenwood Manuals > VR-409

Feb 03, 2016 | Kenwood Audio & Video Receivers

2 Answers

Dead SA-HE 100

hi due to it being lightnig strike their could be that much wrong with it that you might never find the problem.
If you are going to try and repair it then your going to need a multimeter and also get hold of the schematics so you can follow them and for any part numbers you might need.
The chances are its going to be several blown resistors because the lightning strike causing power surge so i would start looking around the board where the power lead goes into the board this would be a good place to start testing

Feb 13, 2008 | Panasonic SA-HE100 Receiver

1 Answer

Hi i have a kenwood system which has a loud hum/buzz over the vol this is louder on radio basically unable to hear any music / speach the hum also is on all other selections cd tape aux record deck mo

This sounds like an earth loop, try discounting the earth in the record deck 13 amp plug. If this works reconnect earth and get a stereo isolating transformer to go between the output of the record deck and Kenwood amp. Remember disconnecting the earth can be dangerous if you don't know what you are doing, best to just disconnect the RCA leads from the deck to start with. To explain an earth loop it's when you have more than one earth point e.g. amp with a earth and record deck with a earth or a CD deck. You can get the transformer from marlin.

Sep 09, 2014 | Audio & Video Receivers

1 Answer

Sound system keeps cutting off. Red flashing light over power button

Take it in to a Kenwood service centre. You can't possibly diagnose what has been damaged by the power spike. At least it is not totally fried and they usually are. You are lucky.

Aug 31, 2014 | Kenwood VR-405 Receiver

2 Answers

My kenwood reciever kr-a4070 keeps blowing a fuse

have you tried a different outlet? something my be wrong internally

Jul 31, 2012 | Kenwood Audio & Video Receivers

1 Answer

Kenwood Tuner/amp. KR-V6090 I need a transformer [not the power transformer], labelled L07-2129-05 S7F2M Existing unit is o/c in the primary Where can I get one please ?

I'm sure you've already seen that the only hits online for the characters "L07-2129-05 S7F2M" are your post.

Try searching for "Kenwood parts" and make some calls.

Sep 21, 2011 | Kenwood VRS-7100 Receiver

1 Answer

Kenwood VR-509 Receiver won't power up...

Check all your speaker wires for shorts, especially behind the amp, doesn't take much for something to throw a spanner in the works, like when cleaning house and moving stuff around.

Oct 03, 2009 | Kenwood VR-509 Receiver

1 Answer

TX-SR803 with no sound or popping hissing on any input

It is common for a short term power surge to open up the internal fuse in the main power transformer. Without testing some components inside the unit, I really can't say for sure whether or not the unit is worth repair. I would suggest that you invest in a detailed repair estimate at an authorized Onkyo service center.

Keep us posted.


May 26, 2009 | Onkyo TX-SR803 Receiver

1 Answer

Unit won't power up completely

The clicks you hear are the relay that completes the circuit for 110V AC to the main power transformer. Mine had the same problem and here's how I've gotten it to work. A lightning strike near our house caused it to fail, and I traced it to the power transformer relay activation circuit. The tuner and amp were fine. I found a bad transistor in the relay circuit, but didn't have a replacement on hand, so I soldered a jumper wire across the relay switch connections on the power transformer circuit board. This connects the 110V AC directly to the power transformer. DC Power to the amp and tuner circuits will still be controlled by the power switch, but the transformer will be supplying all the AC voltages to the main board. If there is a real problem with the circuits that load the transformer or the transformer itself, then the fuse will blow. If the fuse doesn't blow then I suspect the problem is just in the power sequencing circuit itself, that is not needed for operation other than to make the unit "Energy Star Compliant". A lot of electronic items have a transformer that is not switched, and only fused, so that the supplies are available at all times.

Jan 24, 2008 | Audio & Video Receivers

1 Answer


Have a service shop check out your protection IC and related network...accordianman

Sep 06, 2006 | JVC RX-554V Receiver

Not finding what you are looking for?
Kenwood VR-407 Receiver Logo

Related Topics:

595 people viewed this question

Ask a Question

Usually answered in minutes!

Top Kenwood Audio & Video Receivers Experts


Level 2 Expert

49 Answers


Level 1 Expert

28 Answers


Level 1 Expert

13 Answers

Are you a Kenwood Audio and Video Receiver Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides