pm1.5

[woodworks 5]

It all started with some free time and nothing to do. Next thing you know Carver pops into my head while I am on Ebay and well you know the rest of the story. Took a chance on a hr 752 "for parts only" and when it showed up it was like new without a scratch and works perfectly. O K now I'm hooked. My next purchase I did not get that lucky. Bought a pm1.5 "for parts only" hoping it was only the broken fuse holder. replaced fuse holder

powered it up and there is a clicking sound. protection light is on and left meter light is flashing at top of scale. it sounds like the clicking is coming from the transformer.

I am pretty good with electricity I only have a small knowledge about electronics. I looked at some of the m1.5 posts and did some basic testing. appears there is output from the transformer but that is where it stops. very little if any power to the test points listed by Les. No power to large caps. no power to fan.

 

If any one has any ideas or can point me in the right direction I would be thankful.

This is my first post I am looking to acquire some more amazing Carver equipment. This is my first post and I look forward meeting some like mined people

[zumbini 6,140]

Howdy woodworks and welcome to the forum. Nice to have you onboard the Carver train.

 

I'm no more technically-oriented than you are but someone who is should be along shortly to get you started.

[wrf 3,817]

Welcome.

 

The service manual for the PM1.5 is available here. It has an excellent troubleshooting section and rather thoroughly explains how the amp works. It is well worth saving. The primary suspects would be the dual can caps hiding underneath the input board. They are a known weak point. A kit is available from Les to replace them with standard caps. However, it well worth a few tests to confirm the problem rather than just swapping caps and hoping for the best. Many PM amps have led a hard life and suffer from multiple problems.

 

Be careful poking around inside the amp. The big caps can remain charged for quite some time and will damage you or other amp components if you stick a probe crosswise - even with the power OFF. And speaking of OFF, unplug it, don't just turn it off when working on it. Much of the power supply remains energized even with the switch in the OFF position.

[kingman 662]

Welcome to the forum and good luck with the amp repair!

[fill35U 1,845]

Welcome! Nice score with the clean amp. Lucky that you have an identical, working amp to use as a reference, that can help a lot when troubleshooting. Good luck!

[woodworks 5]

Hi everyone,

 

Thanks to all you who welcomed me to the sickness.

 

I have bee looking around the site to glean some repair info on my pm1.5 I tested some of the voltages according to some pictures on les's post about m1.5 recapping and they are not close to spec and two test points have no voltage at all. I started to take the caps out and see that it looks like they have been replaced at some time. my question is could they have gone bad again or is there another problem. when you power up the amp the protection light is on, the left meter is pegged there is a clicking noise that sounds like it is coming from the transformer, and both speakers make a erratic popping noise. If any one has a suggestion I would be thankful. I am not electronically inclined but I am also not afraid to give it a try. Anybody close to Michigan that would repair it if I cannot find the problem

[fill35U 1,845]

It is entirely possible for the replacement capacitors to have failed. How *probable* that is depends on the type of capacitors, when they were installed, and how the amp was run since then.

 

If replacing the caps for the main rails doesn't solve your problem, you will probably want to obtain a Variac to begin further troubleshooting. 

 

When you get to a point that you're unsure, start a thread in the appropriate forum, and we'll try to help as best we can. And at that point you can also see about getting some local help. 

[woodworks 5]

I tried to upload a foto but 192k is all I could reduce it to

[zumbini 6,140]

I tried to upload a foto but 192k is all I could reduce it to

Most of us never use the ATTACH PHOTO TO POST option for just that reason (limited size).

Try using the INSERT IMAGE applet which allows photos up to 14MB and auto resizes to 800x600.

For instructions go to the INSERTING MEDIA section of the FORUM HELP topic. 

[woodworks 5]

Thanks for the info. I am a newbie to the whole forum thing I have never posted anywhere before

[wrf 3,817]

I had a pm1.5 a while back with replacement caps installed backwards! Laugh if you will, but the negative side of the low and mid rail supplies were both backwards. Both caps had vented and the amp was going in and out of protection. The amp suffered from a multitude of other problems as well. It's a hard life on the road.

 

You mention the amp is clicking. That usually means the amp has detected a problem (the service manual says which ones) and is going into protection. Basically turning itself off. After sitting for a few moments turned off, it forgets there is a problem and turns itself back on only to discover the problem didn't go away. It then turns itself off again. The clicking you hear is the mag coil energizing and denergizing. Your voltage measurements will be unstable when this is happening.

 

You may get lucky replacing the caps, but if not you will need a variac to diagnose your problem.

[Circuits & Concepts 311]

Hello, and welcome to the site!

 

You said that you measured the supply voltages per the photo I posted in the other thread. Could you share both the DC and AC measurements? These measurements are taken at the rectifier diodes because they are the most convenient point at which to probe.

 

Thanks!

 

Les