Tremoverb reverb gremlins

[thinskin57]

i've got a '99 tremoverb that is starting to do strange things reverb-wise. basically, the reverb is getting weak. there's no real pattern to when it occurs. sometimes it happens shortly after powering up, sometimes it takes 15 minutes or so. sometimes i could play for a haf-hour to 45 minutes straight with no problems. when the problem occurs, it's as if the reverb is set to the 9:30 position no matter where i turn the reverb knob. i CAN turn it totally off still, but there is no significant difference in the amount of reverb between the aforementioned 9:30 position and having it dimed. so it's not dying out completely, but rather, just weakening. sometimes if i throw the amp on standby for a a few seconds, and then turn the amp back on, i'll get the reverb back for a minute or so before it gets weak again. all my tubes are brand new. i did change out the reverb/V5 tube for another tube but the problem persisted. i also reseated the RCA jacks that go to the reverb. still the problem persists. any ideas?

 

[94Tremoverb]

Is it on both channels? Mine did the same thing, on the red channel only. It was a LDR switch. I had one go down in the channel cloning circuit too... they're a bit of a PITA to change.

If it's on both channels it could be V1, which is the reverb return as well as the input gain stage.

 

[thinskin57]

Is it on both channels? Mine did the same thing, on the red channel only. It was a LDR switch. I had one go down in the channel cloning circuit too... they're a bit of a PITA to change.

If it's on both channels it could be V1, which is the reverb return as well as the input gain stage.

mine's been doing it on the orange channel. then again, i never use reverb in the red channel so i'll have to check it out at practice tomorrow and see if it's doing it on both or not. from what i've read, the LDR's seem to be the achilles heel of these amps. what exactly are they? are they a small component? i've got pics of the inside of my amp's chassis. if i were to email a pic to you, would you be able to identify these for me? thanks.

 

[94Tremoverb]

The LDRs are black components about 1/2" long x 3/8" wide, like a flattened cylinder, with four wires coming from them, two from each end. They're in stacks two to four high in some places. Identifying the correct one will need the schematic and the printing on the circuit board - and due to sod's law, it's pretty much a certainty that the one you need to change will be at the bottom of the stack, which means temporarily undoing all the ones above... not that difficult, but a bit fiddly. LDR7 is the orange channel reverb switch, if it helps!

They could well be the Achilles heel of these amps. They do seem to have a tendency to fail after a number of years - not often, but there are no less than 25 in the Tremoverb, so the chance of one going out at some point is not all that remote. The problem sometimes is even to know one has gone - a lot of them do non-obvious things or operate only in some mode configurations, so if the amp is basically working, but just not sounding right in one mode or another, it's possible it's an LDR that's responsible.

 

[thinskin57]

The LDRs are black components about 1/2" long x 3/8" wide, like a flattened cylinder, with four wires coming from them, two from each end. They're in stacks two to four high in some places. Identifying the correct one will need the schematic and the printing on the circuit board - and due to sod's law, it's pretty much a certainty that the one you need to change will be at the bottom of the stack, which means temporarily undoing all the ones above... not that difficult, but a bit fiddly. LDR7 is the orange channel reverb switch, if it helps!

They could well be the Achilles heel of these amps. They do seem to have a tendency to fail after a number of years - not often, but there are no less than 25 in the Tremoverb, so the chance of one going out at some point is not all that remote. The problem sometimes is even to know one has gone - a lot of them do non-obvious things or operate only in some mode configurations, so if the amp is basically working, but just not sounding right in one mode or another, it's possible it's an LDR that's responsible.

thanks for the info. you know, i had a feeling that's what those were! (LDR's) never seen anything like them in my other amps so i was suspicious that that's what they were. thanks again. we'll see what i find...

 

[mikey383]

The LDRs are black components about 1/2" long x 3/8" wide, like a flattened cylinder, with four wires coming from them, two from each end. They're in stacks two to four high in some places. Identifying the correct one will need the schematic and the printing on the circuit board - and due to sod's law, it's pretty much a certainty that the one you need to change will be at the bottom of the stack, which means temporarily undoing all the ones above... not that difficult, but a bit fiddly. LDR7 is the orange channel reverb switch, if it helps!

They could well be the Achilles heel of these amps. They do seem to have a tendency to fail after a number of years - not often, but there are no less than 25 in the Tremoverb, so the chance of one going out at some point is not all that remote. The problem sometimes is even to know one has gone - a lot of them do non-obvious things or operate only in some mode configurations, so if the amp is basically working, but just not sounding right in one mode or another, it's possible it's an LDR that's responsible.

thanks for the info. you know, i had a feeling that's what those were! (LDR's) never seen anything like them in my other amps so i was suspicious that that's what they were. thanks again. we'll see what i find...

Mesa seemed to use them instead of relays. They're a light dependent resistor, which consists of a photocell switch and a small LED inside a lightproof housing. Two wires are the LED, and the other two are the photocell. When the LED turns on, the photocell detects the light and switches off (or on, depending on the LDR).

They're to blame for a plethora of problems in the TOVs. I recall hearing it was because of their placement near heat emitting parts, but can't say for sure.

 

[94Tremoverb]

In theory they are superior to relays because they're noiseless, allow precise control of the switching speed, and don't need as much current to operate.

But the newer Mesa designs have gone back to using relays, which aren't speed-controllable and then need extra timed mute circuitry to prevent the pops from the contacts coming through, and yet not cause 'drop out', which involves a new set of headaches... so there must be a very good reason the LDRs were abandoned, and I'm pretty sure this is it.

I think this is a major difference between the two and three channel Dual Rectos as well - twos have LDRs, threes have relays. Whether that has anything to do with the tone difference I don't know.

 

[thinskin57]

The LDRs are black components about 1/2" long x 3/8" wide, like a flattened cylinder, with four wires coming from them, two from each end. They're in stacks two to four high in some places. Identifying the correct one will need the schematic and the printing on the circuit board - and due to sod's law, it's pretty much a certainty that the one you need to change will be at the bottom of the stack, which means temporarily undoing all the ones above... not that difficult, but a bit fiddly. LDR7 is the orange channel reverb switch, if it helps!

They could well be the Achilles heel of these amps. They do seem to have a tendency to fail after a number of years - not often, but there are no less than 25 in the Tremoverb, so the chance of one going out at some point is not all that remote. The problem sometimes is even to know one has gone - a lot of them do non-obvious things or operate only in some mode configurations, so if the amp is basically working, but just not sounding right in one mode or another, it's possible it's an LDR that's responsible.

i though the LDR's were to strictly control switching type functions. No? things like channel switching, reverb on/off, trem on/off, loop on/off, etc.

 

[thinskin57]

i'm going to hijack my own thread and ask an unrelated question to you fellow tverb owners who've responded- do your tverbs get hot too? i played mine (combo) w/my band today for the first time for about 2.5 hours, putting it in standby every half-hour or so for short breaks and whatnot. when we were done i was surprised at how hot it was. while this may seem like a "duh" question, i only ask because i had a tverb combo back in 1994 when they first came out and i don't remember it really getting hot at all. if i remember correctly, i was almost disappointed that it didn't get that hot because i thought that's what they were supposed to do! (this was my first tube amp at the time. rookie!) my present tverb combo was pretty hot today though. not scary hot- i've had other tube amps that got as hot, or hotter. it's just that i swear that my recollection of this amp was that it ran cool. maybe my '94 was just different for some reason, idunno. how 'bout you guys?

 

[94Tremoverb]

Mine gets pretty hot, especially the power transformer - not dangerously so, but near the upper end of what I would think of as normal and safe - and it does definitely sound better the longer it's left on.

The LDRs do control switching - on/off functions like the reverb and tremolo, but also the gain and voicing changes between all the modes... that's how it's done, these amps are not really two-channel amps at all, it's a single channel with switching at multiple points in the signal path to add in different resistors, caps etc. It's the different combinations of these that allow the channel cloning as well as the switching, which is why it's such a special feature of these amps - but if one LDR stops working, one or more of the modes will not sound quite right or different from the others, even though it will still actually work. There's also one to couple the tremolo to the signal path, so if the tremolo stops working or gets weak, it's probably this one.

 

[thinskin57]

Mine gets pretty hot, especially the power transformer - not dangerously so, but near the upper end of what I would think of as normal and safe - and it does definitely sound better the longer it's left on.

The LDRs do control switching - on/off functions like the reverb and tremolo, but also the gain and voicing changes between all the modes... that's how it's done, these amps are not really two-channel amps at all, it's a single channel with switching at multiple points in the signal path to add in different resistors, caps etc. It's the different combinations of these that allow the channel cloning as well as the switching, which is why it's such a special feature of these amps - but if one LDR stops working, one or more of the modes will not sound quite right or different from the others, even though it will still actually work. There's also one to couple the tremolo to the signal path, so if the tremolo stops working or gets weak, it's probably this one.

you seem to really know your stuff when it comes to this amp. thanks for all the info!

 

[mikey383]

The LDRs do control switching - on/off functions like the reverb and tremolo, but also the gain and voicing changes between all the modes... that's how it's done, these amps are not really two-channel amps at all, it's a single channel with switching at multiple points in the signal path to add in different resistors, caps etc. It's the different combinations of these that allow the channel cloning as well as the switching, which is why it's such a special feature of these amps - but if one LDR stops working, one or more of the modes will not sound quite right or different from the others, even though it will still actually work. There's also one to couple the tremolo to the signal path, so if the tremolo stops working or gets weak, it's probably this one.

You know, I've looked at the schematics a thousand times and never realized that it's basically the same channel. I see it now that you mentioned it.


I can't comment on the heat issue, as I have a regular DR, but my power transformer does get hot.

 

[UltraGary]

The bolts that hold the handle on the top of my T-Verb combo get SCORCHING hot!

 

[thinskin57]

Is it on both channels? Mine did the same thing, on the red channel only. It was a LDR switch. I had one go down in the channel cloning circuit too... they're a bit of a PITA to change.

If it's on both channels it could be V1, which is the reverb return as well as the input gain stage.

spoke to marcus at boogie tech support today. he said that the LDR's generally don't die slowly, but rather, in one shot. what's your take on this statement? whereas my problem is still intermittent, i've decided to wait until it worsens before i ship it to boogie. he told me that the bad batch of LDR's that they got was from a company called Solonics (spelling?) and if a Tverb has that brand in them, that they replace ALL of them to play it safe. said he was pretty sure that there was no printing on them to identify them as Solonics, but i might take a peak inside the chassis anyway to double-check.