Recapping and repairing a Harman Kardon 730 twin power series stereo receiver

[dlucy]

@sfox52 asked me to recap his hk 730 twin series and since finishing that last week, someone else is asking for the recap BOM, so I'm posting that part quickly here and I'll fill in the details and the input-panel-repair and ps-for-LED-pointer-replacement goodies when I have more time.

Index to some of the useful posts in this thread:

• BOM list of the electrolytic caps you should replace
• BOM list of all transistors that can be (but don't have to be) replaced
• Replacing the bar-style heatsink on the power amp board
• Important comment about replacement transistors on the bar-style heatsink on the power amp board
• Layout of the replacement transistors on the power amp board
• Which power reservoir caps can be used
• Modding the Harman Kardon 730 phono stage to stop using IEC and go back to RIAA
• Difference between IEC (stock in hk730) and RIAA (standard everywhere else)
• Comments about how a restored&upgraded hk730 sounds:
  • Recapping and repairing a Harman Kardon 730 twin power series stereo receiver
  • Recapping and repairing a Harman Kardon 730 twin power series stereo receiver
  • Recapping and repairing a Harman Kardon 730 twin power series stereo receiver

Elsewhere:

• Updated BOM with replacements for my parts that are now EOL HK730 Rebuild - Observations

Thanks very much to the following AK'ers contributing to this thread (and the many others):

@quaddriver​

@Skywatcher​

@Pete B​

@jheu02​

@sfox52​

@Flounder​

 

[dlucy]

The obligatory before image and nudies:

 

[dlucy]

As usual, I replaced a lot more than just the electrolytic caps, but here is the BOM for just those. note: this is a rushed list. you should double-check this before ordering:

Board Qty Type Sub-type value 1 value 2 purpose mouser PN
EQ (PHONO) 2 Capacitor Electrolytic 0.1 uF 35 V signal 505-MKP2D031001F00KI
EQ (PHONO) 2 Capacitor Electrolytic 1 uF 50 V signal 505-MKS2C041001F00MI
EQ (PHONO) 2 Capacitor Electrolytic 100 uF 10 V signal 647-UKL1A101MED1TD
EQ (PHONO) 2 Capacitor Electrolytic 22 uF 10 V signal 647-UKL1E220MDDANATA
EQ (PHONO) 2 Capacitor Electrolytic 220 uF 25 V power 647-UPW1E221MPD1TD
EQ (PHONO) 2 Capacitor Electrolytic 33 uF 10 V signal 647-UKL1V220MEDANA
Main rectifier 4 Capacitor Electrolytic 2200 uF 16 V power 647-UPW1C222MHD
Main rectifier 1 Capacitor Electrolytic 470 uF 16 V power 647-UPW1E471MPD6
power amp 4 Capacitor Electrolytic 100 uF 10 V signal 647-UKL1A101MED1TD
power amp 4 Capacitor Electrolytic 1000 uF 10 V signal 647-UKL1A102KHD
power amp 2 Capacitor Electrolytic 220 uF 6.3 V signal 647-UKL1A221MPDANA
Power supply (two PS on one board) 4 Capacitor Electrolytic 4700 uF 50 V power 647-UFW1H472MRD
Selector top board 2 Capacitor Electrolytic 100 uF 10 V signal 647-UKL1A101MED1TD
Tone control and local rectifier 2 Capacitor Electrolytic 1.5 uF 35 V signal 505-MKS2C041501H00KI
Tone control and local rectifier 2 Capacitor Electrolytic 100 uF 10 V signal 647-UKL1A101MED1TD
Tone control and local rectifier 4 Capacitor Electrolytic 1000 uF 25 V power 647-UPW1E102MHD
Tone control and local rectifier 4 Capacitor Electrolytic 22 uF 16 V signal 647-UKL1E220MDDANATA
Tone control and local rectifier 2 Capacitor Electrolytic 220 uF 6.3 V power 647-UPW1E221MPD1TD
tuner 2 Capacitor Electrolytic 0.22 uF 35 V signal 505-MKS2D032201C00KI
tuner 2 Capacitor Electrolytic 0.33 uF 35 V signal 505-MKS2C033301C00JI
tuner 3 Capacitor Electrolytic 0.47 uF 35 V signal 505-MKS2D034701E00JI
tuner 3 Capacitor Electrolytic 10 uF 16 V signal 647-UKL1H100MDDANA
tuner 1 Capacitor Electrolytic 100 uF 10 V signal 647-UKL1A101MED1TD
tuner 3 Capacitor Electrolytic 220 uF 16 V power 647-UPW1E221MPD1TD
tuner 2 Capacitor Electrolytic 3.3 uF 25 V signal 647-UKL1H3R3MDDANA
tuner 2 Capacitor Electrolytic 4.7 uF 25 V signal 647-UKL1H4R7MDDANA ​

Cut-and-paste list (for Mouser.com's BOM tool):

647-UPW1E102MHD 4
647-UPW1E221MPD1TD 7
647-UPW1C222MHD 4
647-UPW1E471MPD6 1
647-UFW1H472MRD 4
505-MKP2D031001F00KI 2
505-MKS2D032201C00KI 2
505-MKS2C033301C00JI 2
505-MKS2D034701E00JI 3
505-MKS2C041001F00MI 2
505-MKS2C041501H00KI 2
647-UKL1H100MDDANA 3
647-UKL1A101MED1TD 11
647-UKL1A102KHD 4
647-UKL1E220MDDANATA 6
647-UKL1A221MPDANA 2
647-UKL1H3R3MDDANA 2
647-UKL1V220MEDANA 2
647-UKL1H4R7MDDANA 2 ​

 

[JMiP]

Never heard of a BOM tool before and I'm finding out now that it's...well...the bomb!

 

[sfox52]

I have barely had a chance to listen to it, but I am so glad that Doug was able and willing to do the work on this old HK. I plan on listening to it for many years to come.

 

[Oerets]

So just how much trouble was this unit to work on?

I have a working 930 and thought someday of doing PM on.

 

[dlucy]

The layout makes it very easy to work on. The one obstacle that I didn’t overcome was removing the selector knob shaft that runs from the front panel nearly to the back panel. It seems designed to disengage, but I could not get it loose without applying more force than I was comfortable with. Desoldering the caps with pads under that shaft was a challenge because the shaft remained in the way.

 

[Oerets]

Cool!

Mine works great just not used alot.

Someday maybe get to the recap stage, it sounds so nice now. Can only imagine how much better it would be if I did.

Really under the radar IMHO the whole HK units are is seems.

 

[Oldsansui441]

Nice work dlucy .

 

[Reliving.]

View attachment 1645115

As usual, I replaced a lot more than just the electrolytic caps, but here is the BOM for just those. note: this is a rushed list. you should double-check this before ordering:

Board Qty Type Sub-type value 1 value 2 purpose mouser PN
EQ (PHONO) 2 Capacitor Electrolytic 0.1 uF 35 V signal 505-MKP2D031001F00KI
EQ (PHONO) 2 Capacitor Electrolytic 1 uF 50 V signal 505-MKS2C041001F00MI
EQ (PHONO) 2 Capacitor Electrolytic 100 uF 10 V signal 647-UKL1A101MED1TD
EQ (PHONO) 2 Capacitor Electrolytic 22 uF 10 V signal 647-UKL1E220MDDANATA
EQ (PHONO) 2 Capacitor Electrolytic 220 uF 25 V power 647-UPW1E221MPD1TD
EQ (PHONO) 2 Capacitor Electrolytic 33 uF 10 V signal 647-UKL1V220MEDANA
Main rectifier 4 Capacitor Electrolytic 2200 uF 16 V power 647-UPW1C222MHD
Main rectifier 1 Capacitor Electrolytic 470 uF 16 V power 647-UPW1E471MPD6
power amp 4 Capacitor Electrolytic 100 uF 10 V signal 647-UKL1A101MED1TD
power amp 4 Capacitor Electrolytic 1000 uF 10 V signal 647-UKL1A102KHD
power amp 2 Capacitor Electrolytic 220 uF 6.3 V signal 647-UKL1A221MPDANA
Power supply (two PS on one board) 4 Capacitor Electrolytic 4700 uF 50 V power 647-UFW1H472MRD
Selector top board 2 Capacitor Electrolytic 100 uF 10 V signal 647-UKL1A101MED1TD
Tone control and local rectifier 2 Capacitor Electrolytic 1.5 uF 35 V signal 505-MKS2C041501H00KI
Tone control and local rectifier 2 Capacitor Electrolytic 100 uF 10 V signal 647-UKL1A101MED1TD
Tone control and local rectifier 4 Capacitor Electrolytic 1000 uF 25 V power 647-UPW1E102MHD
Tone control and local rectifier 4 Capacitor Electrolytic 22 uF 16 V signal 647-UKL1E220MDDANATA
Tone control and local rectifier 2 Capacitor Electrolytic 220 uF 6.3 V power 647-UPW1E221MPD1TD
tuner 2 Capacitor Electrolytic 0.22 uF 35 V signal 505-MKS2D032201C00KI
tuner 2 Capacitor Electrolytic 0.33 uF 35 V signal 505-MKS2C033301C00JI
tuner 3 Capacitor Electrolytic 0.47 uF 35 V signal 505-MKS2D034701E00JI
tuner 3 Capacitor Electrolytic 10 uF 16 V signal 647-UKL1H100MDDANA
tuner 1 Capacitor Electrolytic 100 uF 10 V signal 647-UKL1A101MED1TD
tuner 3 Capacitor Electrolytic 220 uF 16 V power 647-UPW1E221MPD1TD
tuner 2 Capacitor Electrolytic 3.3 uF 25 V signal 647-UKL1H3R3MDDANA
tuner 2 Capacitor Electrolytic 4.7 uF 25 V signal 647-UKL1H4R7MDDANA ​

Cut-and-paste list (for Mouser.com's BOM tool):

647-UPW1E102MHD 4
647-UPW1E221MPD1TD 7
647-UPW1C222MHD 4
647-UPW1E471MPD6 1
647-UFW1H472MRD 4
505-MKP2D031001F00KI 2
505-MKS2D032201C00KI 2
505-MKS2C033301C00JI 2
505-MKS2D034701E00JI 3
505-MKS2C041001F00MI 2
505-MKS2C041501H00KI 2
647-UKL1H100MDDANA 3
647-UKL1A101MED1TD 11
647-UKL1A102KHD 4
647-UKL1E220MDDANATA 6
647-UKL1A221MPDANA 2
647-UKL1H3R3MDDANA 2
647-UKL1V220MEDANA 2
647-UKL1H4R7MDDANA 2 ​

Wish you could do this service for me because l find ordering parts a nightmare....it must take hours to order Caps for a big Amp.... have you done a AKAI AA1175

Did Amp sound cool when finished.... it’s has 2 transformers!!. What Caps do you like.

 

[dlucy]

l find ordering parts a nightmare....it must take hours to order Caps for a big Amp....

To order the parts you just cut-and-paste the above BOM list into the BOM Tool at Mouser.com. It makes ordering very easy.

 

[Reliving.]

Do Mouser deal with the UK .

 

[Hyperion]

Do Mouser deal with the UK .

In a word - yes.

https://www.mouser.co.uk/

 

[Reliving.]

In a word - yes.

https://www.mouser.co.uk/

Great stuff....
Doug , there are 3 different coloured Caps in the the old Amp as a newbie did the Company’s from 70,s use different types of the capacitors like we use now... yes we have more choices now.

I see the black and grey ones a lot,but in my AKAI AA1175 there are some yellow ones from Amps from Japan.

Also the very small blue ceramic Caps, why do you like to change these little beasts.

Doug what are repairing next .. keep us updated.

 

[JMiP]

To order the parts you just cut-and-paste the above BOM list into the BOM Tool at Mouser.com. It makes ordering very easy.

I noticed last night when I tried the BOM tool that I had to be logged into my Mouser account. If you don't have one already, create one, log into it, then run copy/pasted text into the tool and you are off and running. It populates the shopping cart with those items for you. It's amazing.

 

[dlucy]

Great comments. Let’s please focus on the topic itself, HK 730 recap.

 

[dlucy]

Also the very small blue ceramic Caps, why do you like to change these little beasts

The oval-shaped, pea-sized, robin egg blue colored, hard shelled caps are tantalum caps. They were a compromise in the past, not great for signal path, and other issues can be found here on AK by searching for tantalum. I replace them on sight.

 

[Hyperion]

I sometimes wonder why they were used at all in audio equipment, being as they are not good for signal path locations. They are physically small, and very low leakage, and I think I am correct to say very stable over time. So, when replacing them, due consideration should be given as to why they were used. Low leakage seems to be the only attribute which would be valuable in audio equipment, so when replacing them I make sure to use a low leakage replacement - either a low leakage electrolytic or the 'low leakage by their nature', film capacitors.

Their bad reputation comes at least in part from their tendency to fail short circuit, with attendant local circuitry damage, thankfully a rare occurrence. One more thing, they absolutely don't like reverse voltage.

 

[JMiP]

Any thoughts on modding the EQ/phono board per this thread?

 

[dlucy]

Ok, now that I've had time to organize the photos and my notes, here goes.

The improved basic nudie photos, inside and outside the harman kardon 730 twin power series (or hk730 in case someone searches for it like that).

The outsides continue the 330A/330B/330C minimalist styling.










The "twin power" series has two power supplies, each with dual rails, each feeding one channel of the power amp.

And it has the condensed, FM + AM + MPX functions all on a single tuner board.



The 730 still has the secondary rectifier board from prior generations.

It also has a long-shaft function selector ending in a multi-layer wafer switch on the rear of the chassis: