Cerwin Vega P1800/P1500 schematic

[mikeskory]

Does anyone know how to find Cerwin Vega schematics? I have a P1800 powered sub here for learning purposes. I believe the P1800 is the same as the P1500. I'm having no luck finding schematics on line.

[Enzo]

Hi Mike. Did we call CV direct and ask about it?

US Contact Information:
PRO AUDIO / HOME AUDIO USA:
Gibson Customer Service

Phone: 1-800-4GIBSON (1-800-444-2766)

E-mail: Gibson Customer Service

[mikeskory]

Ok...I found myself with a weekend of so I decided to learn about PMPS popwer supplies. So I was impatient! Lol! I'll do it Monday.

[Enzo]

One major warning. Most all SMPS you will see rectify the mains DIRECTLY, meaning 340vDC with all the current in the world just asking to kill you. But on the primary side there are often little ICs controlling things, and they run on like 12v or 5vDC. But the "ground" in that primary side is actually the -170v DC rail, from the mains rectifier. SO you cannot ground your scope to that "ground". Schematic usually has a different symbol got that ground or at least a designation like GNDH. (H for high voltage)

[mikeskory]

Thanks for the reminder. I but have a bad habit of touching things. I checked the voltage across a typical looking bridge rectifirer. Just like you said it's 330 volts. If I get a schematic I should be able to find the IC called the PULSE WIDTH MODULATOR. What I really don't understand is where does the 5v DC or 12v DC come from that runs the MODULATOR section? There is a small transormer next to the main transformer. On TV screens I understand that is the remote control (or stand-by) power. Maybe the small transormer supplies the MODULATOR IC as well?? I'll keep listening to the you tubes and hopefully have a schemo tommorrow. It would feel good to get this working!

[Enzo]

See if you can find a schematic, I hope this is not one of the ICE modules - no support for them.

on MANY SMPS, there will be a high resistance from the V+ (+170) down to the IC + lead. This is a trickle start. Resistors maybe 470k? A pair of 150k? That is enough to get a couple cycles out of the IC, and once running, some little winding on the transformer makes a tiny 5v or 12v supply for the UC. It powers itself in other words. That is typically just an extra winding on an existing transformer, not a stand alone little transformer. Mostly.

[vintagekiki]

https://music-electronics-forum.com/showthread.php?t=50492

https://music-electronics-forum.com/showthread.php?t=50493


Hi mikeskory
No need to spam thread with same request.
One Schematic Requests is sufficient for same schematic.
Thanks for understanding.

vk

1) Same request in two threads. Reason for deleted
https://music-electronics-forum.com/showthread.php?t=50493

[mikeskory]

That was quick. Cerwin-Vega! says NO. No schematics except for authorized dealers. They do not operate a repair facility. The only one in Michigan is Vision Electronics in Allen Park.
BUT I don't think it's the power supply curcuit now. I tried to measure the voltages on the secondary of the main transformer using the (-) of the bridge but got nothing. Without the schemo I didn't wan't to guess. BUT there are 4 2200mf caps feeding the outputs. I get 80 v on all 4 of those caps.

[Jazz P Bass]

" I tried to measure the voltages on the secondary of the main transformer using the (-) of the bridge".
Whoa Nellie.
Most SMPS 's have the primary supply and the secondary supply isolated.
It would be wise to use a common node of the secondary for true voltage measurements.

[vintagekiki]

http://www.cerwinvega.com/manuals/pro/P1500XP1800SXManual%20REVC_EnglishWEB.pdf

Try to follow Troubleshooting page 26

[mikeskory]

Ok Vintage Kid, I see what you're getting at. I'll make sure of the symptom by following the troubleshooting guide. It's back together now. BTW When I tested the voltage on the 4 2200mf caps I just went pos to neg at each cap. I checked the big 18" for ohms only when I first started but never heard it play. I'll get back to everyone later.

[Enzo]

Only the primary side is referenced to the -170v rail. The secondary stuff is all referenced to circuit ground.

And be aware that SMPS operate at super high frequency, like 50kHz or 100kHz. So your meter cannot detect that. A scope would.

[mikeskory]

I put it back together a couple days ago then I tested the speaker again. Then I set the amp back into the cabinet. It's been playing for the few days at low to medium volumes. The only thing I did to the boards was reflow all 6 big caps, the bridge and the switching FETS. So I don't know...the customer insists it smelled and quit playing.

[Enzo]

If the customer knew what was going on, maybe he would have fixed it himself. You're an experienced pro, trust yourself.