• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Marantz 4230 blowing fuse

ocdecio

ocdecio

The proof of the restoring is in the listening.
Subscriber
I got this 4230 and I found out the bridge rectifier was shorted, therefore fuses would immediately blow. I replaced it with a compatible bridge and turned it on with a DBT. The 100W light dimmed but not as much as it does with other receivers such as the 2225 and 2230. The dial lights came on, somewhat dimmed.

Could it be that there is yet another issue down the line that is actually causing the bridge rectifier to fail at some point? I am thinking maybe the filter capacitor (there is only one) may be a problem?

In your experience - with these quad receivers, should the DBT dim as much as the regular stereo units? This is only 30wpc in bridged mode.

Any words of wisdom would be very much appreciated.


upload_2021-9-8_21-20-13.png
 
Register to hide this ad
It won't dim as much, remember a 2 channel receiver has 4 outputs (referencing the units you mentioned) , a 4 channel typically has 8 so you are pulling double the current at idle with a quad. A BRIGHT bulb would indicate a short, this isn't what you are seeing now that the bridge has been replaced. You didn't mention Bias, is it biasing properly? If you are worried about the main cap replace it, it's not an expensive cap and there's only one.
 
bktheking said:
It won't dim as much, remember a 2 channel receiver has 4 outputs, a 4 channel typically has 8 so you are pulling double the current at idle with a quad. A BRIGHT bulb would indicate a short, this isn't what you are seeing now that the bridge has been replaced. You didn't mention Bias, is it biasing properly?
Click to expand...
Indeed, this one has 8 2SD315s - not big transistors but still 8 of them as you mention. I also read somewhere around here that all boards in this receiver are powered on no matter if they are being used or not.

Now - would it be OK to try running it at low volume with the DBT just to make sure I can get some sign of life before plugging it to the wall? I measured the filter cap, it seems OK and with the dbt I am getting around 37V across it.
 
Wait - this amp looks like capacitor coupled so there should be no DC anyway? There is no trimpot to adjust DC. It has two big 3300uf caps on each board connected to what looks like a zobel network:

upload_2021-9-9_10-13-47.png
 
I connected the speakers and some input to AUX. It works for a couple of seconds (music comes out of both speakers) but a hum shows up and then the light starts to oscilate.

Is it possible that these amps have odd behavior because they are not being given proper voltage/power and oscillation may be one of the symptoms?

How safe would it be for me to just connect it to the wall, any suggestions on anything I should do or check beforehand? The output transistors are not shorted, I checked all of them.
 
ocdecio said:
...Is it possible that these amps have odd behavior because they are not being given proper voltage/power and oscillation may be one of the symptoms?...
Click to expand...
I've seen this due to the lower line voltage. Go for it!

I'd have meters measuring the bias and switch as after a minute or so before any long term test just to be sure. I'd replace that main filter soon too as wisely mentioned already.
 
Yep the thing is working on all cylinders now. It just has a "whoosh" on startup, maybe a recap would help? After a couple of seconds it sounds just like a Marantz should.
 
You must log in or register to reply here.
Back
Top Bottom