Questions about servicing and powering up a Harman Kardon 630 for the first time in 30 years

[Calania]

Hello, I recently inherited a old Harman Kardon 630 from my grandfather. They bought it new and was always super careful with there stuff and were really happy with it but "upgraded" to a black plastic pioneer in the late 80s and since then the Harman has been siting in it's box in a closet for 30 year and hasn't been powered up since then. It is in amazing condition cosmetically and hasn't got a single scratch on it or the wood but I am a little afraid to connect it to power since it's been so long.

What I'm thinking of doing is to fist remove the cover and see if I can see something wrong with the capacitors. Then build a dim bulb tester and power it up. Then measure dc offset and if that's okay then connect it to a pair of crap speakers I have to see if they work.

Does this sound like a good plan? I have seen some people use variable voltage device but that's nothing I own. Anything else I should do? Don't know if it matters but I am in Europe so it's 230V for me.

I plan on doing a complete recapping on it and will probably do it myself but it will probably take me a few weeks to order the parts and find the time to sit down and do it. In the meantime would you say it's safe-ish to use it with my good speaker or do I run a risk of damaging them?

Lastly the thing that makes me consider taking it to a service tech instead of repairing it myself is that in the past I have struggled with un-soldeing parts. I have a big hatred towards solder suckers and even though I have soldered a lot in the past I could easily count the number of times I have been able to de-solder something with a solder sucker on one hand. I have been thinking about buying a inexpensive electric solder sucker like this one. Does any body have any experience with these? https://www.kjell.com/globalassets/...ef=6F748C2C10&format=jpg&w=960&h=960&mode=pad

 

[painttoad]

honestly, that generation of HK's have delicate traces. it's not something that you want to mess with if you have trouble desoldering parts.

your method of pre-power up is good.

 

[mrk229]

You are on the right track.
A thorough visual inspection top and bottom is a great place to start.
Look at the large caps for any signs of venting/leakage.
Check the speaker fuses for correct value and type and that they are good.
Checking DC offset is always a good idea for a new to you amp/receiver.
Definitely power it up with a Dim-Bulb.
When you first power it up check the amplifier heat sinks several times over a few minutes for excessive heat, especially if they heat rapidly.
Odds are pretty good that the switches and pots will need some attention.

I have not used that type of solder sucker before but it is a "manual" version of the higher end models.
Two differences, It is a "one shot" not continuous vacuum as the big boys.
And second and more importantly is from what I can see it is not temperature regulated which in my experience is very important,
Heck probably the most important feature of any soldering iron, solder sucker. Too much heat will quickly damage and lift traces.

 

[painttoad]

I have not used that type of solder sucker before but it is a "manual" version of the higher end models.
Two differences, It is a "one shot" not continuous vacuum as the big boys.
And second and more importantly is from what I can see it is not temperature regulated which in my experience is very important,
Heck probably the most important feature of any soldering iron, solder sucker. Too much heat will quickly damage and lift traces.

i bought one, used it a few times. i had to take a file to the shaft as it would not stay engaged.

they are really awkward to use. i went back to the manual sucker and soldering iron before i got a pump.

when they work they are ok.

 

[Calania]

Thanks for the answers and tips. Since I solder quite a lot I have been tempted for a long time to buy a solder sucker with a vacuum pump and with adjustable temperature but I have always thought they were to expensive for how rarely I de-solder stuff. Maybe this is the time for me to take the plunge? How easy would you say it is to damage a trace when using one of those?

 

[painttoad]

Thanks for the answers and tips. Since I solder quite a lot I have been tempted for a long time to buy a solder sucker with a vacuum pump and with adjustable temperature but I have always thought they were to expensive for how rarely I de-solder stuff. Maybe this is the time for me to take the plunge? How easy would you say it is to damage a trace when using one of those?

it still happens. they are not the end all solution of desoldering. you still need a manual pump and wick and know how and when to use them.

asking questions helps but practice is the only way to get experience.

adding solder before desoldering always helps

 

[Calania]

Okay will see what I do. Hoping for a sale on those fancy vacuums sucker after christmas. I have a very good service guy 30 minutes from where I live and he has been running that store since the 70s so he knows what he is doing. I might as well at least talk with him and see what he would charge. But the main reason that I want to do it myself is not because of money but because I want to learn how to do it and I enjoy project like this. I just don't know if this is the unit I want to learn on.

 

[painttoad]

Okay will see what I do. Hoping for a sale on those fancy vacuums sucker after christmas. I have a very good service guy 30 minutes from where I live and he has been running that store since the 70s so he knows what he is doing. I might as well at least talk with him and see what he would charge. But the main reason that I want to do it myself is not because of money but because I want to learn how to do it and I enjoy project like this. I just don't know if this is the unit I want to learn on.

where are you located at?

i'd give you a parts unit to practice on if you were close. on that same note, hit up thrift stores and find a beater you can practice on.

 

[Calania]

Thanks, that's really nice of you! I however live in Sweden and looking at your profile it seems like we are a bit to far from each other for that to be viable. But great advice with the thrift store. If I don't feel like hunting for a good deal they always at least have some crap no name receiver laying around for 15 €. I might also ask the service guy I talked about before if he has some scrap boards I could buy/get to practice on

 

[Oerets]

Take it over and have it serviced up if sentimental attachments at all apply.
Then if wanting to do servicing in the future be looking for a unit to purchase and practice on may be the way to go.

 

[MX117.MC7150]

This stuff works great - https://www.amazon.com/solder-wick/s?k=solder+wick
Get a small size for fine work and a larger size for heavier work. Unless you have a pro-model, solder suckers, quite literally, suck.

Solid-state power supplies should not be brought up on a Variac. The power supply tries to provide full rail voltage regardless of input voltage. The result is that it will draw whatever current it can to do so (P = I x E) and could burn something that would normally be fine. Best to simply turn it on. If you do use a Variac, then turn it up to full voltage fairly quickly.

BTW - the HK 630 is worthy piece. Fond memories of mine in the late '70s driving a pair of Polk 7's.

 

[Guido57]

Having recently been able to borrow what seems like a pretty serious Tenma desoldering station I will attest to there being a learning curve. The person who lent it to me advised that cleanup with wick is usually still needed. That said, anywhere there is a large amount of solder these are a blessing. Much easier than using a spring loaded sucker.

 

[mea2112]

Solid-state power supplies should not be brought up on a Variac. The power supply tries to provide full rail voltage regardless of input voltage. The result is that it will draw whatever current it can to do so (P = I x E) and could burn something that would normally be fine. Best to simply turn it on. If you do use a Variac, then turn it up to full voltage fairly quickly.

I always thought using a variac to power on anything solid-state was considered the best way and would not cause any problems?

 

[Mumbles]

I always thought using a variac to power on anything solid-state was considered the best way and would not cause any problems?

Me to. At the moment I'm also working on a HK 630 Twin which I purchased with a known dead short in it somewhere. When I first powered it up, I used both a DBT and a Variac with two DVM's hooked up to the rails. Rail voltages came up corresponding to the amount of input to the transformers. It couldn't produce the specified 32V if I tried.

 

[Bill Ferris]

Over the past 47 yrs. of servicing audio equipment, I always very, very slowly variac up the voltage over a number of hrs. any "closet queen" brought to me.
That has been dormant for yrs./decades while monitoring it`s mains current draw and primary filter caps temperature.

Solid state amplifiers will have no load/speakers/head phones hooked up while the amp is very slowly brought up towards it`s design input voltage.

Tube amplifiers, preamps, and tuners dormant resurrection procedure is similar, but requires a substitution of the tube rectifier, if used, with SS for initial very, very slow mains voltage ramp up.
This has seemed to minimize any chance of damage to components within the equipment, and needless exploding main power supply electrolytic capacitors, or stressing/shorting out the SS rectifiers, and blowing the device`s fuse(s)

Just my method that has successfully worked very well, for me over the many yrs.

Feel free to chose this or your own method !

 

[painttoad]

i like the dim bulb myself. it will tell me of excessive current draw immediately.

my variac does not have an ammeter so i have it plugged into a kilowatt to monitor current.

but not all units can be brought up on a dim bulb. i recently had a pioneer sa-950 on the bench. it was screwing with my brain. the dim bulb indicating a dead short and i could not find one and it was supposed to be a working unit.

i finally put it on the variac. brought it up slow and the relay kicked in and all was golden.

 

[Bill Ferris]

i like the dim bulb myself. it will tell me of excessive current draw immediately.

my variac does not have an ammeter so i have it plugged into a kilowatt to monitor current.

but not all units can be brought up on a dim bulb. i recently had a pioneer sa-950 on the bench. it was screwing with my brain. the dim bulb indicating a dead short and i could not find one and it was supposed to be a working unit.

i finally put it on the variac. brought it up slow and the relay kicked in and all was golden.

I have had a kilowatt for yrs. but a bit of high input voltage has to become high enough for the kilowatt`s display to operate, so one is blind to the current/wattage draw of the DUT, unless the kilowatt monitor has been modified to have it`s internal circuitry separately AC powered up during the variac voltage ramping up !
Until I could afford to purchase full metered variacs for my benches, I just used a selectable amp sensitivity clamp on AC ampmeter, with or without its included plug in current loop adaptor to monitor the DUT`s current draw.

Though yrs. ago I bought all the items to build a 3 position multi wattage bulb DIM current limiter, I have yet to assemble it !

I guess with the decades of metered variac use with situational awareness, luck and a deft hand on the voltage knob during ramp up, just never thought it was necessary in my trouble shooting bench needs!

 

[painttoad]

I have had a kilowatt for yrs. but a bit of high input voltage has to become high enough for the kilowatt`s display to operate, so one is blind to the current/wattage draw of the DUT, unless the kilowatt monitor has been modified to have it`s internal circuitry separately AC powered up during the variac voltage ramping up !

i have a "suraielec" kilowatt meter. seems to be pretty responsive pretty fast. it is powered by the mains. it shows mains voltage but not voltage being drawn, which kinda sucks. it shows wattage and amperage but you have to cycle thru to see them. it would be ideal if everything was one the screen at the same time.

all good. variac has an analog voltmeter. the variac was an ebay special. it all works well for me.

 

[PF Sound]

I bought one of these about a month ago & have used it several times.

Amazon.com

It works pretty good but isn't perfect.......no heat control, no on/off switch, just an led that shows it's on, & only two small tips included. Also, the "sucker" tube itself is suspect. The suction is adequate, & you get a couple extra O-rings with it but I've had to clean it & lube it with some wd40 a couple times. It's a step up from using an iron & separate sucker but I don't think I'd trust it on a "delicate" PCB.

 

[sregor]

Get some liquid rosin based flux and a small paint brush - makes soldering and desoldering much easier. Non acid flux. Check before buying or using.
Also a second for bringing it up slowly on a variac. Used for many years - only problems come when there is a soft start circuit - (even that can be gotten around if you bypass the soft start and monitor the current. Not for noobies....)