Just acquired HEATHKIT W4-AM-*picture*

[Dominick22]

Link and pic of amp here:

http://www.heathkit-museum.com/hifi/w4-am.shtml

First, I'd like to hear opinions if you know about this amp.
This amp is in great shape but when I fired it up, the fuse blew.

I was told that replacing the caps would probably cure the amp completely. The problem is that I don't what caps it uses!

Has anyone else gone through this maintenance that ca offer advice/parts list?

Thanks,
Dominick

PS-Its my first tube and I cant wait

 

[Trout]

I Had one of those for a bit, For sure you will need to replace that Can Style Multisection eyectrolytic. Even if it tested marginally, It can and will be a problem down the road.

AES is a fair source for those metal can caps in many cases they are exact matches. though not especially cheap. Mallory FP Style Can Caps

Instantly blowing a fuse might be something more serious though. Bad Rect Tube, Shorted transformer and on and on. Mine had a bad can cap and a blown resistor.

Trout

 

[Alain Dupont]

dominik22,

Here is a link to the schematic:

http://www.geocities.com/free_schematic/amplifier/heathkit/w4schematic.html

Caps to be replaced:

- All electrolytics {power supply }
4 * 20 microF 450 Volts
2 * 20 microF 350 volts

Coupling caps to be replaced:

All...

Tubes:
All tubes 2 * 6SN7 - 2 * 5881 - 1 * 5Y4G

Resistors:
All cathode and Anode resistors ; plus verify all the others...

Good DIY.

Alain.

 

[Dominick22]

Thanks for the help!

Dominick

 

[terminatorx]

Same Problem

One of my Heath 44-AM amps started blowing fuses as well. I brought it to a shady shop in Toronto and they guy said the transformer was shorted. 2 questions;

1. How can I verify this with a multimeter
2. What options do I have for a replacement?

Cheers,
Noah

 

[Tom Bavis]

If the fuse blows INSTANTLY, it's a shorted transformer or rectifier (probably socket). Shorted cap wouldn't blow fuse until the rectifier warms up.

Hammond makes replacement transformers - about $80 - or you can try for a used one if you want to keep the appearance original.

 

[SY]

Terminatorx, disconnect all leads and check the primary and secondary coil resistances for dead shorts. The secondary should be checked from center tap to each end- the values should be within 15% of one another. Check resistance from each lead to the case- it should be open circuit. (an analog ohmmeter works best here)

Now CAREFULLY connect the primary to the AC line using a series fuse (or, what I use, a 60W light bulb). Load the secondary with a voltmeter. Apply power. If the fuse pops immediately (or the light bulb lights), you've got a bad tranny. If it doesn't and you get a high value of voltage (for this tranny, end to end will be something like 700V), the transformer is likely OK.

edit: This test exposes LETHAL voltages. If you have ANY doubts whatever about your abilities or experience, don't do it! Death is very permanent.

 

[Dominick22]

Your edit came too late...Now I am dead! Thanks for the help!

Dominick

 

[Sherman]

Don't join the club!

http://www.ibiblio.org/Dave/Dr-Fun/df9510/df951017.jpg

 

[terminatorx]

Thanks for the info. 3 quick follow up questions;

1. Any idea where I can find an original tranformer, or a W4-AM for parts?

2. should I attempt to rewind the transoformer?

3. If I replace the transformer with a 3rd party unit, will I need to replace the transformer on the other mono-block to ensure they both sound the same?

Cheers,

 

[Dominick22]

I am now actively trying to fix the W4-Am and I am having troubel reading the schematics I have seen.

Does anyone have a link to a clearer picture. Maybe the building instructions even for the original kit???

I don't know what parts to buy and what goes where!
Thanks,
Dominick

 

[anatech]

Hi Dominick,
PM me. My schematic seems to be clear.

terminatorx,
What does your transformer smell like? I have a lot on my plate right now, but I can have a look later if you wish. I am not that far away from you.

-Chris

 

[imonti]

I have one of these W4 - AM

If any one wants to buy my W4-AM from me before I ebay it...(going for around 200 on ebay). contact me make me a offer.. I also have the preamp and tuner by Heathkit . I bought them all a while back and never used them, I really just wanted the Mullards from the preamp...anyway if you are interested. contact me... its a lot better than rewiring your blown unit

 

[Dominick22]

Can you send some pics of all the parts???

I havent seen the preamp-so I am especially curious about it!

Thanks,
Dominick

 

[terminatorx]

2nd blown amplifier

Thanks all for the advice. So my first amp is in a shop with someone whom I dont trust.

In the mean time, my second amplfier started blowing fuses. After some troubleshooting, I determined that there is a short across the primary winding. So my question is this. Is it a reasonable for both transformers to blow within 1 month of eachother? Both are original.

Thanks,

Noah

 

[anatech]

Hi Noah,
If you measure the primary circuit with a normal ohm meter, you will read a low resistance (a few ohms or so). That is perfectly normal.

It is not reasonable to have transformers shorting out all by themselves.

So my first amp is in a shop with someone whom I dont trust.

Why don't you trust them? If you have good reason not to trust the tech, remove the amp. You wouldn't let a mechanic you don't trust repair your car, would you? Just make sure you are being reasonable.

-Chris

 

[terminatorx]

Chris.

As for the audio shop, something just does not feel right there, hard to put my finger on it. At any rate I've desided to brush off my engineering text books and give it a try on my own. The primary coil reads ~2.8 ohms, however it pops the fuse even when I had all the secondary disconnected. Its just a little strange that both my amps blew a power suppy transformer within 1 month of eachother.

So aside from the correct taps and voltages, and form factor, is there anything I should look for in a power supply transformer?

Thx,

Noah

 

[anatech]

Hi Noah,
2R8 sounds okay for a power transformer primary measuring with DC.
Measure from each side to chassis. I see there is both an octal socket and accessory outlet that is supplied with raw AC power.

If you disconnect one lead from the primary you can try to apply power again. I would be using a variac to apply partial power and slowly ramp up while watching the current meter.

I wouldn't right the power transformer off just yet. Also check for added disc caps and other undocumented things connected to the AC supply or transformer.

If you want to swing by at some point we can have a quick peek to see for sure.

-Chris

 

[Voiceoftheatre]

Heathkit W4 B tube Amp Fuse Blowing

Hi,
I'm sort of new at this site and saw that you had problems with your W4.
I have a good operating W4. I was got interested in your problem So I flipped mine over, pulled the rectifier and took DC measurements on the trany. Heres how I measured it.

Primary Windings

Unpug the unit from the wall socket,
unplug the preamp (if you have one),
pull the fuse
measure at the AC receptical outlet on the amp.
You shoul get a reading of 3.5 ohms +or- 10%.
check the reading from the recepticle to the chassis.
The reading should be infinite.
If you have any reading at all you might have a bad trany
Before you condem the trany make sure the recepticle has no shorts to chassis.

Secondary Windings
Heaters

Pull all the remainder tubes and measure from pin 7 to pin 8 of any 6SN7
the reading should be about .3 Ohms
Measue from any one of those pins to the chassis
the reading should be about half of the .3 Ohms

High voltage windings

With the rectifier still out
At the rectifier socket measure from pin4 to pin 6 (remember you read the socket upside down)
Your reading should be 120 Ohms
Measure from pin 4 of the rectifier to ground
Mesurement should be about 60 Ohms +or- 10%
Measure from Pin 6 of the rectifier to ground
You should ge another reading of 60 Ohms +or- 10%
If you have a lesser reading YOU HAVE A Bad Trany.

Now With the rectifier still out
Measure from pin 2 to pin 8
You should get a reading of approx .3ohms
I would not recommend a reading from these pins to the chassis due to the filters and choke would confuse the reading.
If you want to further check out this winding you have to unsolder the filters on pin 8 of the rectifier resocket.


That should pretty much check out your power trany If every thing checks out I would start looking at the filters, One could be a dead short
A final word, Heathkit used some healthy Transformers, I've always admired their ruggedness.

Hope this helps
Good luck
VOT